ETC MC1241A

Advanced Microstepping
Motion Control Chipset
Features
Internal generation of microstepping signals
2-phase as well as 3-phase stepper motors
64 microsteps per full step
S-curve, trapezoidal, and velocity profile
trajectory modes
Incremental encoder feedback
On-the-fly motor stall detection
Software & feature compatible with other
versions of PMD's chipset family
Available in 1 or 2 axis configurations
32-bit position, velocity, acceleration and jerk
trajectory profile registers
Electronic Gearing
Two travel-limit switches per axis
Choice of PWM or DAC motor output signals
Chipset Developer's Kit Available
Microstepping Waveforms
Phase B
90 Deg
Microsteps
64
128
192
256
3-Phase Stepper
Phase A
120 Deg
Phase B
Phase C
General Description
The MC1241A is a dedicated motion processor which functions as a
complete chip-based stepper motor controller. Packaged in a 2-IC
chipset, this device performs trajectory profile generation and
microstepping signal generation. The chipset outputs PWM or
DAC-compatible motor command signals which directly drive the
windings of the stepping motor, eliminating the need for external
microstepping circuitry. The MC1241A also provides the ability to
input incremental encoder signals. It is available in a one, or a two-axis
configuration.
The MC1241A is functionally similar to other members of PMD's 1st
Generation Motion Processor Family however it adds the ability to
perform micrstepping signal generation. All of these devices provide
sophisticated trajectory generation allowing the creation of complex
motion sequences.
2-Phase Stepper
Phase A
MC1241A
MC1141A
320
Both two and three-phase stepping motors are supported by the
MC1241A. An internal ROM-based lookup table is used to generate
the microstepping waveforms. The motor power level can be controlled
with a resolution of 16 bits. Changes to the motor power level can be
coordinated with other profile changes to optimize motor heat
dissipation under different load and acceleration conditions.
The chipset is controlled by a host processor which interfaces with the
chipset via an 8-bit, bi-directional port. Communications to/from the
chipset consist of packet-oriented messages.
The chipset is packaged in 2 68-pin PLCC packages. Both chips utilize
CMOS technology and are powered by 5 volts.
Doc. Rev. 11.03, Nov 1997
Performance Motion Devices, Inc. 12 Waltham St. Lexington, MA 02421 tel: 781.674.9860 fax: 781.674.9861 www.pmdcorp.com
Table of Contents
Host Interrupts.......................................................Page 28
Encoder Position Feedback ..................................Page 29
High Speed Position Capture............................Page 29
Position Capture ReadBack ..............................Page 29
Stall Detection ...................................................Page 29
Position Error ....................................................Page 30
Recovering From A Motion Error ......................Page 30
Microstepping........................................................Page 30
Microstepping Waveforms.................................Page 31
Motor Command Control...................................Page 31
AC Induction Motor Control...............................Page 31
Command Summary .........................................Page 32
Motor Output .........................................................Page 32
Motor Output Signal Interpretation ....................Page 32
DAC16 Decoding...............................................Page 32
PWM Decoding .................................................Page 32
Motor Drive Configurations ...............................Page 33
3-Phase Drive Configuration .............................Page 33
Host Commands .....................................................Page 34
Command Summary .............................................Page 34
Command Reference ............................................Page 36
Axis Control.......................................................Page 36
Profile Generation .............................................Page 37
Parameter Update.............................................Page 41
Interrupt Processing ..........................................Page 43
Status/Mode ......................................................Page 44
Motor Control ....................................................Page 45
Encoder.............................................................Page 46
Miscellaneous ...................................................Page 48
Microstepping....................................................Page 49
Application Notes ...................................................Page 52
Interfacing MC1241A to ISA bus...........................Page 52
PWM Motor Interface ............................................Page 54
16-Bit Serial DAC Motor interface .........................Page 56
Product Family Overview....................................... Page 3
Introduction........................................................... Page 3
Family Summary................................................... Page 3
Electrical Characteristics....................................... Page 4
Absolute Maximum Ratings.................................. Page 4
Operating Ratings................................................. Page 4
DC Electrical Characteristics ................................ Page 5
AC Electrical Characteristics ................................ Page 5
I/O Timing Diagrams............................................. Page 7
Pinouts .................................................................... Page 12
MC1241A, MC1141A Pinouts............................... Page 12
Pin Descriptions.................................................... Page 13
Theory of Operations ............................................. Page 17
Operational Parameters ....................................... Page 18
Trajectory Profile Generation................................ Page 18
S-curve Point to Point....................................... Page 19
Trapezoidal Point to Point................................. Page 20
Velocity Contouring........................................... Page 20
Electronic Gear................................................. Page 21
Trajectory Control .......................................................... Page 21
Halting The Trajectory ...................................... Page 21
Motion Complete Status ................................... Page 22
Parameter Loading & Updating ............................ Page 22
Manual Update ................................................. Page 22
Breakpoints....................................................... Page 23
Disabling Automatic Profile Update .................. Page 23
Travel Limit Switches........................................ Page 23
Axis Timing ........................................................... Page 24
Host Communications .......................................... Page 25
Electrical Interface ............................................ Page 25
Packet Format .................................................. Page 25
Packet Checksum............................................. Page 26
Illegal Commands............................................. Page 26
Command Errors .............................................. Page 26
Axis Addressing................................................ Page 27
Axis Status............................................................ Page 27
Status Word...................................................... Page 27
Miscellaneous Mode Status Word .................... Page 27
Performance Motion Devices, Inc. does not assume any responsibility for use of any circuitry described in this manual, nor does it make
any guarantee as to the accuracy of this manual. Performance Motion Devices, Inc. reserves the right to change the circuitry described in
this manual, or the manual itself, at any time.
The components described in this manual are not authorized for use in life-support systems without the express written permission of
Performance Motion Devices, Inc..
2
Product Family Overview
# of axes
Motors Supported
Encoder Format
Output Format
S-curve profiling
Electronic gearing
On-the-fly changes
Limit switches
PID & feedforward
PWM output
DAC-compatible output
Pulse & direction output
Index & Home signal
Chipset p/n's
Developer's Kit p/n's:
MC1401 series
4, 2, or 1
DC Servo
Incremental (no dash version)
and Parallel ('-P' version)
DC servo
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
MC1401A, MC1401A-P (4 axes)
MC1201A, MC1201A-P (2 axes)
MC1101A, MC1101A-P (1 axis)
DK1401A, DK1401A-P
MC1231 series
2 or 1
Brushless Servo
Incremental
MC1241 series
2 or 1
Stepper
Incremental
MC1451 series
4, 2, or 1
Stepper
Incremental (-E version)
Sinusoidally
commutated
Yes
Yes
Yes
Yes
Yes
Yes
Yes
Yes
MC1231A (2 axes)
MC1131A (1 axis)
Microstepping
Pulse and Direction
Yes
Yes
Yes
Yes
Yes
Yes
Yes
MC1241A (2 axes)
MC1141A (1 axis)
DK1231A
DK1241A
Yes
Yes
Yes
Yes
Yes
Yes (-E version)
MC1451A, MC1451A-E (4 axes)
MC1251A, MC1251A-E (2 axes)
MC1151A, MC1151A-E (1 axis)
DK1451A
Introduction
Family Summary
This manual describes the operational characteristics of the MC1241A
and MC1141A Motion Processors. These devices are members of
PMD's 1st generation motion processor family, which consists of 16
separate products organized into four groups.
MC1401 series (MC1401A, MC1201A, MC1101A, MC1401A-P,
MC1201A-P, MC1101A-P) - These chipsets take in incremental
encoder signals (standard version) or parallel word encoder signals
(-P version) and output a motor command in either PWM or DACcompatible format. These chipsets come in 1, 2 or 4 axis versions
and can be used with DC brushed motors, or brushless motors using
external commutation.
Each of these devices are complete chip-based motion controllers.
They provide trajectory generation and related motion control functions.
Depending on the type of motor controlled they provide servo loop
closure, on-board commutation for brushless motors, and high speed
pulse and direction outputs. Together these products provide a
software-compatible family of dedicated motion processor chips which
can handle a large variety of system configurations.
MC1231 series (MC1231A, MC1131A) - These chipsets take in
incremental quadrature encoder signals and output sinusoidally
commutated motor signals appropriate for driving brushless motors.
They are available in one or two axis versions. Depending on the
motor type they output two or three phased signals per axis in either
PWM or DAC-compatible format.
Each of these chips utilize a similar architecture, consisting of a highspeed DSP (Digital Signal Processor) computation unit , along with an
ASIC (Application Specific Integrated Circuit). The computation unit
contains special on-board hardware such as a multiply instruction that
makes it well suited for the task of motion control.
MC1241 series (MC1241A, MC1141A) - These chipsets provide
internal microstepping generation for stepping motors. They are
available in a one or a two-axis version. Two phased signals are
output per axis in either PWM or DAC-compatible format. An
incremental encoder signal can be input to confirm motor position.
Along with a similar hardware architecture these chips also share most
software commands, so that software written for one chipset may be reused with another, even though the type of motor may be different.
MC1451 series (MC1451A, MC1251A, MC1151A, MC1451A-E,
MC1251A-E, MC1151A-E) - These chipsets provide very high speed
pulse and direction signal output appropriate for driving step motorbased systems. They are available in a one, two, or four-axis version
and are also available with quadrature encoder input.
This manual describes the operation of the MC1241A and
MC1141A chipsets. For technical details on other members of
PMD's 1st generation motion processors see the corresponding
product manual.
Each of these chipsets has an associated Chipset Developer's
Kit available for it. For more information contact your PMD
representative.
3
Interconnections between the two chips consist of a data bus and
various control and synchronization signals. The following table
summarizes the signals that must be interconnected for the chipset to
function properly. For each listed signal the I/O chip pin on the left side
of the table is directly connected to the pin to the right.
Electrical Characteristics
Overview
I/O Chip Signal
Name
CPData4
CPData5
CPData6
CPData7
CPData8
CPData9
CPData10
CPData11
CPAddr0
CPAddr1
CPAddr2
CPAddr3
CPCntr0
CPCntr1
CPCntr2
CPCntr3
CPWrite
CPClk
The MC1241A consists of two 68 pin PLCC's both fabricated in CMOS.
The Peripheral Input/Output IC (I/O chip) is responsible for interfacing
to the host processor and to the position input encoders. The Command
Processor IC (CP chip) is responsible for all host command, trajectory,
and microstep computations, as well as for outputting the PWM and
DAC signals.
The following figure shows a typical system block diagram, along with
the pin connections between the I/O chip and the CP chip.
Motor
(2 axis)
Encoder
(1-2 axis)
Amplifier
(1-2 axis)
Data4-11
I/OAddr0-3
I/O
I/OWrite
I/O Chip
Pin
18
5
6
7
8
17
3
1
68
27
29
12
20
36
22
63
2
46
CP Chip
Signal Name
Data4
Data5
Data6
Data7
Data8
Data8
Data10
Data11
I/OAddr0
I/OAddr1
I/OAddr2
I/OAddr3
I/OCntr0
I/OCntr1
I/OCntr2
I/OCntr3
I/OWrite
ClkOut
CP Chip
Pin
50
49
46
43
40
39
36
35
28
9
6
5
16
18
68
67
15
19
CP
For a complete description of all pins see the 'Pin Descriptions'
section of this manual.
I/OCntrl0-3
ClkOut
Absolute Maximum Ratings
Host
Processor
Unless otherwise stated, all electrical specifications are for both
the I/O and CP chips.
The CP and I/O chips function together as one integrated motion
processor. The major components connected to the chip set are the
optional encoder (2, or 1 axes), the motor amplifier (2, or 1 axes), and
the host processor.
Storage Temperature, Ts.....................-55 deg. C to +150 deg. C
Supply Voltage, Vcc.............................-0.3 V to +7.0 V
Power Dissipation, Pd..........................650 mW (I/O and CP
combined)
The encoder signals are input to the I/O chip in quadrature format. Two
signals encode the position, and an optional index signal contains a
once-per-rotation locating signal.
Operating Ratings
The chipset's motor output signals are connected to the motor amplifier.
Two types of output are provided; PWM (pulse width modulation), and
DAC-compatible signals used with an external DAC (digital to analog
converter). In addition 2-phase as well as 3-phase stepping motors are
supported. Because the output signals are in microstepping format, two
phased signals are provided per axis, with the relative phasing of the
two signals depending on the motor type (2-phase or 3-phase).
Operating Temperature, Ta .................0 deg. C to +70 deg. C*
Nominal Clock Frequency, Fclk ...........25.0 Mhz
Supply Voltage, Vcc.............................4.75 V to 5.25 V
* Industrial and Military operating ranges also available. Contact your
PMD representative for more information
The host processor is interfaced via an 8-bit bi-directional bus and
various control signals. Host communication is coordinated by a
ready/busy signal, which indicates when communication is allowed.
4
DC Electrical Characteristics
(Vcc and Ta per operating ratings, Fclk = 25.0 Mhz)
Symbol
Vcc
Idd
Input Voltages
Vih
Vil
Vihclk
Vihreset
Output Voltages
Voh
Parameter
Supply Voltage
Supply Current
Min.
4.75
Logic 1 input voltage
Logic 0 input voltage
Logic 1 voltage for clock pin
(ClkIn)
Logic 1 voltage for reset pin
(reset)
Logic 1 Output Voltage
2.4
Vol
Logic 0 Output Voltage
Iout
Iin
Iinclk
Tri-State output leakage current
Input current
Input current ClkIn
Max.
5.25
100
Units
V
mA
2.0
-0.3
3.0
Vcc + 0.3
0.8
Vcc+0.3
V
V
V
4.0
Vcc+0.3
V
V
-20
-50
-20
0.33
V
20
50
20
uA
uA
uA
Conditions
open outputs
@CP Io = 300 uA
@I/O Io = 4 mA
@CP Io = 2 mA
@I/O Io = 4 mA
0 < Vout < Vcc
0 < Vi < Vcc
0 < Vi < Vcc
AC Electrical Characteristics
(see reference timing diagrams)
(Vcc and Ta per operating ratings; Fclk = 25.0 Mhz)
(~ character indicates active low signal)
Timing Interval
Encoder and Index Pulse Timing
Motor-Phase Pulse Width
Dwell Time Per State
Index Pulse Setup and Hold
(relative to Quad A and Quad B low)
Reset Timing
Stable Power to Reset
Reset Low Pulse Width
Clock Timing
Clock Frequency (Fclk)
Clock Pulse Width
Clock Period
T#
Min.
T1
T2
T3
1.6
0.8
0
uS
uS
uS
0.25
1.0
Sec
uS
6.7
19.5
39
T4
T5
5
Max.
25.6
75 (note 2)
149 (note 2)
Units
Mhz
nS
nS
Timing Interval
Command Byte Write Timing
~HostSlct Hold Time
~HostSlct Setup Time
HostCmd Setup Time
Host Cmd Hold Time
HostRdy Delay Time
~HostWrite Pulse Width
Write Data Setup Time
Write Data Hold Time
Data Word Read Timing
~HostSlct Hold Time
~HostSlct Setup Time
HostCmd Setup Time
HostCmd Hold Time
Read Data Access Time
Read Data Hold Time
~HostRead high to HI-Z Time
HostRdy Delay Time
Read Recovery Time
Data Word Write Timing
~HostSlct Hold Time
~HostSlct Setup Time
HostCmd Setup Time
HostCmd Hold Time
HostRdy Delay Time
~HostWrite Pulse Width
Write Data Setup Time
Write Data Hold Time
Write Recovery Time
DAC Interface Timing
I/OAddr Stable to ~I/OWrite setup time
~I/OWrite Pulse Width
Data Hold Time After ~I/OWrite
ClkOut Low to I/OAddr stable
ClkOut Low to ~I/OWrite Low
ClkOut Low to Data Valid
ClkOut Cycle Time
I/OAddr Stable to DACSlct High
~I/OWrite Low to DACSlct High
PWM Output Timing
PWM Output Frequency
note 1
note 2
note 3
note 4
T#
Min.
Max.
Units
T6
T7
T8
T9
T13
T14
T15
T16
15
10
10
25
2000 (note 3)
nS
nS
nS
nS
nS
nS
nS
nS
T6
T7 (read only)
T8 (read only)
T9
T10
T11
T12
T13
T17
15
- 20
- 20
25
70
50
35
30
2000 (note 3)
50
10
50
70
60
T6
T7
T8
T9
T13
T14
T15
T16
T18
15
10
10
25
2000 (note 3)
70
50
35
30
60
T19
T20
T21
T22
T23
T24
T25
T26
T27
35
56
17
10
75
97.6
95
40
92
92
160 typical (note 4)
66
44.5
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
nS
Khz
~HostSlct and HostCmd may optionally be de-asserted if setup and hold times are met.
Chip-set performance figures and timing information valid at Fclk = 25.0 only. For timing information & performance parameters at Fclk <
25.0 Mhz, call PMD.
Two micro seconds maximum to release interface before chip set responds to command
ClkOut from CP is 1/4 frequency of ClkIn (CP chip).
6
I/O Timing Diagrams
The following diagrams show the MC1241A electrical interface timing. T#' values are listed in the above timing chart.
Quadrature Encoder Input Timing
T1
T1
Quad A
T2
T2
Quad B
T3
T3
~Index
Index = ~A * ~B * ~IND
Clock Timing
ClkIn
T4
T4
T5
7
Command Byte Write TIming
T7
T6
T8
T9
~HostSlct
HostCmd
T14
~HostWrite
T15
HostData0-7
T16
HostRdy
T13
8
Data Word Read TIming
T7
T6
Note 1
~HostSlct
T8
T9
Note 1
HostCmd
T17
~HostRead
T12
HostData0-7
High-Z
High-Z
High
Byte
T10
High-Z
Low
Byte
T11
HostRdy
T13
9
Data Word Write TIming
T7
T6
Note 1
~HostSlct
T8
T9
Note 1
HostCmd
T18
T14
T14
~HostWrite
T15
HostData0-7
T15
High
Byte
Low
Byte
T16
T16
HostRdy
T13
10
DAC Interface Timing
T25
ClkOut
T22
T19
I/OAddr
T23
T20
~I/OWrite
T24
T21
Data 0-11,
DACAddr0,1
T27
T26
DACSlct
11
Pinouts
9
61
1
9
60
10
61
1
60
10
CP
I/O
(Top view)
(Top view)
26
44
27
44
26
43
27
43
MC1241A Pinouts
28
42
24
13
26
30
9
23
33
46
52
45
29
12
2
20
36
22
63
68
27
41
37
4, 21, 25, 38, 55
4, 22, 33
VCC
VCC
QuadA1
QuadB1
Index1
Home1
QuadA2
QuadB2
Index2
Home2
DACSlct
CPClk
I/OClkIn
I/OClkOut
CPAddr2
CPAddr3
CPWrite
CPCntrl0
CPCntrl1
CPCntrl2
CPCntrl3
CPAddr0
CPAddr1
HostCmd
HostRdy
I/O
HostRead
HostWrite
HostSlct
HostIntrpt
HostData0
HostData1
HostData2
HostData3
HostData4
HostData5
HostData6
HostData7
CPData4
CPData5
CPData6
CPData7
CPData8
CPData9
CPData10
CPData11
8
56
7
55
2
54
1
53
30
29
24
19
17
16
18
68
67
64
63
62
61
51
47
48
44
50
61
53
65
67
62
64
60
18
5
6
7
8
17
3
1
PWMMag1A
PWMSign1A
PWMMag1B
PWMSign1B
PWMMag2A
PWMSign2A
PWMMag2B
PWMSign2B
DAC16Addr0
DAC16Addr1
ClkIn
ClkOut
Reset
I/OCntrl0
I/OCntrl1
I/OCntrl2
I/OCntrl3
DACLow0
DACLow1
DACLow2
DACLow3
GND
CP
Data0
Data1
Data2
Data3
Data4
Data5
Data6
Data7
Data8
Data9
Data10
Data11
I/OAddr0
I/OAddr1
I/OAddr2
I/OAddr3
I/OWrite
PosLimit1
PosLimit2
NegLimit1
NegLimit2
60
59
58
57
50
49
46
43
40
39
36
35
28
9
6
5
15
52
45
51
44
Data0
Data1
Data2
Data3
Data4
Data5
Data6
Data7
Data8
Data9
Data10
Data11
I/OAddr0
I/OAddr1
I/OAddr2
I/OAddr3
I/OWrite
PosLimit1
NegLimit1
60
59
58
57
50
49
46
43
40
39
36
35
28
9
6
5
15
52
51
GND
3, 34
14, 15, 32, 49, 54, 66
MC1141A Pinouts
28
42
24
13
33
46
52
45
29
12
2
20
36
22
63
68
27
41
37
4, 21, 25, 38, 55
4, 22, 33
VCC
VCC
QuadA1
QuadB1
Index1
Home1
DACSlct
CPClk
I/OClkIn
I/OClkOut
CPAddr2
CPAddr3
CPWrite
CPCntrl0
CPCntrl1
CPCntrl2
CPCntrl3
CPAddr0
CPAddr1
HostCmd
HostRdy
I/O
HostRead
HostWrite
HostSlct
HostIntrpt
HostData0
HostData1
HostData2
HostData3
HostData4
HostData5
HostData6
HostData7
CPData4
CPData5
CPData6
CPData7
CPData8
CPData9
CPData10
CPData11
51
47
48
44
50
61
53
65
67
62
64
60
18
5
6
7
8
17
3
1
8
56
7
55
30
29
24
19
17
16
18
68
67
64
63
62
61
PWMMag1A
PWMSign1A
PWMMag1B
PWMSign1B
DAC16Addr0
DAC16Addr1
ClkIn
ClkOut
Reset
I/OCntrl0
I/OCntrl1
I/OCntrl2
I/OCntrl3
DACLow0
DACLow1
DACLow2
DACLow3
CP
GND
GND
14, 15, 32, 49, 54, 66
3, 34
12
Pin Descriptions
The following tables provide pin descriptions for the MC1241A-series chipsets.
IC
Pin Name
I/O Chip Pinouts
I/O
QuadA1
QuadB1
QuadA2
QuadB2
Pin #
Description/Functionality
28
42
26
30
Quadrature A, B channels for axis 1 - 2 (input). Each of these 2 pairs of quadrature (A, B)
signals provide the position feedback for an incremental encoder. When the encoder is
moving in the positive, or forward direction, the A signal leads the B signal by 90 degs.
NOTE: Many encoders require a pull-up resistor on each of these signals to establish a
proper high signal (check the encoder electrical specifications)
NOTE: For MC1241A all 4 pins are valid. For MC1141A pins for axes 1 only are valid. Invalid
axis pins can be left unconnected
I/O
~Index1
~Index2
24
9
NOTE: These signals are not required for normal operation, but may be used if desired to
confirm motor position.
Index encoder signals for axis 1-2 (input). Each of these 2 signals indicate the index flag
state from the encoder. A valid index pulse is recognized by the chip set when the index flag
transitions low, followed by the corresponding A and B channels of the encoder transitioning
low. The index pulse is recognized at the later of the A or B transitions. If not used this signal
must be tied high.
NOTE: For MC1241A both pins are valid. For MC1141A pins for axes 1 only are valid.
Invalid axis pins can be left unconnected.
I/O
~Home1
~Home2
13
23
NOTE: These signals are not required for normal operation, but may be used if desired to
confirm motor position.
Home signals for axis 1-2 (input). Each of these signals provide a general purpose input to
the hardware position capture mechanism. A valid home signal is recognized by the chipset
when the home flag transitions low. These signals have a similar function as the ~Index
signals, but are not gated by the A and B encoder channels. For valid axis pins, If not used,
this signal must be tied high. See below for valid pin definitions for the MC1241A and
MC1141A.
NOTE: For MC1241A both pins are valid. For MC1141A pins for axes 1 only are valid.
Invalid axis pins can be left unconnected.
I/O
DACSlct
33
I/O
CPClk
46
I/O
I/OClkIn
52
I/O
I/OClkOut
45
I/O
CPAddr0
CPAddr1
CPAddr2
CPAddr3
68
27
29
12
NOTE: These signals are not required for normal operation, but may be used if desired to
confirm motor position.
DAC Select (output). This signal is asserted high to select any of the available DAC output
channels. For details on DAC decoding see description of DAC16Addr0-1 signals.
I/O chip clock (input). This signal is connected directly to the ClkOut pin (CP chip) and
provides the clock signal for the I/O chip. The frequency of this signal is 1/4 the user-provided
ClkIn (CP chip) frequency.
Phase shifted clock (input). This signal must be connected to I/OClkOut (I/O chip), and inputs
a phase shifted clock signal.
Phase shifted clock (output). This signal must be connected to I/OClkIn (I/O chip), and
outputs a phase shifted clock signal.
I/O chip to CP chip communication address (input). These 4 signals are connected to the
corresponding I/OAddr0-3 pins (CP chip), and together provide addressing signals to
facilitate CP to I/O chip communication.
13
IC
I/O
Pin Name
~CPWrite
Pin #
2
I/O
I/O
CPCntrl0
CPCntrl1
CPCntrl2
CPCntrl3
HostCmd
20
36
22
63
41
I/O
HostRdy
37
I/O
~HostRead
51
I/O
~HostWrite
47
I/O
~HostSlct
48
I/O
~HostIntrpt
44
I/O
I/O
HostData0
HostData1
HostData2
HostData3
HostData4
HostData5
HostData6
HostData7
CPData4
CPData5
CPData6
CPData7
CPData8
CPData9
CPData10
CPData11
Vcc
50
61
53
65
67
62
64
60
18
5
6
7
8
17
3
1
4, 21, 25, 38, 55
I/O
GND
14, 15, 32, 49, 54,
66
I/O
Description/Functionality
I/O chip to CP chip communication write (input). This signal is connected to the ~I/OWrite pin
(CP chip) and provides a write strobe to facilitate CP to I/O chip communication.
I/O chip to CP chip communication control (mixed). These 4 signals are connected to the
corresponding I/OCntrl0-3 pins (CP chip), and provide control signals to facilitate CP to I/O
chip communication.
Host Port Command (input). This signal is asserted high to write a host command to the chip
set. It is asserted low to read or write a host data word to the chipset
Host Port Ready/Busy (output). This signal is used to synchronize communication between
the DSP and the host. HostRdy will go low (indicating host port busy) at the end of a host
command write or after the second byte of a data write or read. HostRdy will go high
(indicating host port ready) when the command or data word has been processed and the
chip set is ready for more I/O operations. All host port communications must be made with
HostRdy high (indicating ready).
Typical busy to ready cycle is 67.5 uSec, although it can be longer when host port traffic is
high.
Host Port Read data (input). Used to indicate that a data word is being read from the chip set
(low asserts read).
Host Port Write data (input). Used to indicate that a data word or command is being written to
the chip set (low asserts write).
Host Port Select (input). Used to select the host port for reading or writing operations (low
assertion selects port). ~HostSlct must remain inactive (high) when the host port is not in use.
Host Interrupt (output). A low assertion on this pin indicates that a host interrupt condition
exists that may require special host action.
Host Port Data 0-7 (bi-directional, tri-stated). These signals form the 8 bit host data port used
during communication to/from the chip set. This port is controlled by ~HostSlct, ~HostWrite,
~HostRead and HostCmd.
I/O chip to CP chip data port (bi-directional). These 8 bits are connected to the corresponding
Data4-11 pins on the CP chip, and facilitate communication to/from the I/O and CP chips..
I/O chip supply voltage pin. All of these pins must be connected to the supply voltage. Supply
voltage = 4.75 to 5.25 V
I/O chip ground pin. All of these pins must be connected to the power supply return.
14
IC
Pin Name
CP Chip Pinouts
CP
PWMMag1A
PWMMag1B
PWMMag2A
PWMMag2B
Pin #
Description/Functionality
8
7
2
1
PWM motor output magnitude signals (output). When the chip set is in PWM output mode
these pins provide the Pulse Width Modulated magnitude signal to the motor amplifier. Two
phases of command signal are output per motor axis, indicated phase A and phase B, with
the axis number indicated 1 or 2.
NOTE: For MC1241A all four pins are valid. For MC1141A pins for axes 1 only are valid.
Invalid axis pins can be left unconnected.
CP
CP
CP
CP
PWMSign1A
PWMSign1B
PWMSign2A
PWMSign2B
PosLimit1
PosLimit2
NegLimit1
NegLimit2
DAC16Addr0
DAC16Addr1
56
55
54
53
52
45
51
44
30
29
The PWM resolution is 10 bits, frequency = 97.6 kHz.
PWM motor output direction signals (output). When the chip set is in PWM output mode
these pins provide the sign signal to the motor amplifier. Two phases of command signals are
output per motor axis, indicated phase A and phase B, with the axis number indicated 1 or 2.
NOTE: For MC1241A all four pins are valid. For MC1141A pins for axes 1 only are valid.
Invalid axis pins can be left unconnected.
Positive limit switch input for axis 1-2. These signals provide directional limit inputs for the
positive-side travel limit of the axis. Upon powerup these signals default to "active high"
interpretation, but the interpretation can be set explicitly using the SET_LMT_SENSE
command. (See Host Command Section for more info.) If not used these signals should be
tied low for the default interpretation, or tied high if the interpretation is reversed.
NOTE: For MC1241A both pins are valid. For MC1141A pins for axes 1 only are valid. Invalid
axis pins can be left un connected.
Negative limit switch input for axis 1-2. These signals provide directional limit inputs for the
negative-side travel limit of the axis. Upon powerup these signals default to "active high"
interpretation, but the interpretation can be set explicitly using the SET_LMT_SENSE
command. (See Host Command Section for more info.) If not used these signals should be
tied low for the default interpretation, or tied high if the interpretation is reversed.
NOTE: For MC1241A both pins are valid. For 1141 pins for axis 1 only are valid. Invalid axis
pins can be left un connected.
Axis Address used during 16-bit DAC motor command output. These signals encode the
motor output axis address as shown in the table below:
Dac16Addr1
Low
Low
High
High
CP
ClkIn
24
Dac16Addr0
Low
High
Low
High
Addressed Encoder
Axis 1 phase A
Axis 1 phase B
Axis 2 phase A
Axis 2 phase B
To write a valid DAC motor command value DACSlct (I/O chip) and I/OAddr0-3 (CP chip)
must be high, and I/OWrite (CP chip) must be low. The 16 bit DAC data word is organized as
follows: High twelve bits are in Data0-11 (CP chip), and low 4 bits are in DACLow0-3 (CP
chip).
Clock In (input). This pin provides the chip set master clock (Fclk = 25.0 Mhz)
15
IC
CP
Pin Name
ClkOut
Pin #
19
CP
~Reset
17
CP
I/OCntrl0
I/OCntrl1
I/OCntrl2
I/OCntrl3
Data0
Data1
Data2
Data3
Data4
Data5
Data6
Data7
Data8
Data9
Data10
Data11
DACLow0
DACLow1
DACLow2
DACLow3
I/OAddr0
I/OAddr1
I/OAddr2
I/OAddr3
16
18
68
67
60
59
58
57
50
49
46
43
40
39
36
35
64
63
62
61
28
9
6
5
I/OWrite
15
CP
CP
CP
CP
Description/Functionality
Clock Out (output). This pin provides a clock output which is 1/4 the ClkIn frequency. This pin
is connected to I/OClkin (I/O chip).
Master chip set reset (input). When brought low, this pin resets the chip set to its initial
condition. Reset should occur no less than 250 mSec after stable power has been provided
to the chip set.
I/O chip to CP chip communication control (mixed). These signals are connected to the
corresponding CPCntrl0-3 pins on the I/O chip, and provide control signals to facilitate CP to
I/O communication.
Multi-purpose Data0-11. (Bi-directional). These pins have 2 functions:
1) Pins Data4-11 (8 bits total) are connected to the corresponding CPData4-11 pins on the
I/O chip, and are used to communicate between the CP and I/O chips
2) Pins Data0-11 hold the high 12 bits of the DAC output value when the output mode is set
to 16-bit DAC.
DACLow0-3 (output). These pins hold the lowest 4 bits of the 16 bit DAC output word when
the output mode is set to 16 bit DAC. These pins, in conjunction with Data0-11 (providing the
high 12 bits) make up the 16-bit DAC output word.
Multi-purpose Address0-3 (output). These pins are connected to the corresponding CPAddr03 pins on the I/O chip. They have 2 functions; They provide addressing signals to facilitate
communication between the I/O chip and CP chip, and they are used during DAC data
decoding. To read a valid DAC value from Data0-Data11 (CP chip), DACSlct (I/O chip) and
I/OAddr0-3 (CP chip) must all be high, and I/OWrite (CP chip) must be low.
Multi-purpose write (output). This pin is connected to CPWrite on the I/O chip. It has 2
functions:
1) It provides a control signal to the I/O chip to facilitate communication between the I/O chip
and CP chip.
CP
Vcc
4, 22, 33
CP
GND
3, 34
2) It is used during DAC data decoding to read a valid DAC value from Data0-Data11 (CP
chip), DACSlct (I/O chip) and I/OAddr0-3 (CP chip) must all be high, and I/OWrite (CP chip)
must be low.
CP chip supply voltage pin. All of these pins must be connected to the supply voltage. Supply
voltage = 4.75 to 5,.25 V
CP chip ground pin. All of these pins must be connected to the power supply return.
16
Theory of Operations
Internal Block Diagram
Incremental Encoder
Index Home
1/a
Motor Output
B
A
1/a
1/a
PWM mag. PWM dir.
1/a
DAC address
DAC data
2
1/phase
16
PWM, DAC signal generator (2-4 channels)
Microstepping
Generator (2)
Quadrature
decoder
counter (2)
Trajectory profile
generator (2)
Index capture
register (2)
System Registers (2)
Host command
Host I/O controller
5
Control
8
Data
1/a
1
host interrupt
PosLimit
Host I/O
1/a
NegLimit
Over-travel Inputs
The above figure shows an internal block diagram for the MC1241A
motion processor.
The sine-wave microstepping signals are output in PWM format with a
separate magnitude and sign signal per phase, or as a digital word with
up to 16 bits of resolution that is constructed externally into an analog
signal using a DAC. In DAC mode two address bits indicate which of
the two axes and two phases are being loaded by the chipset.
Each axis provides programmable trajectory generation including
electronic gearing, trapezoidal point-to-point, and s-curve point to point
moves. In addition the chipset contains an internal microstepping signal
generator. The microstep generator outputs 2 phased signals per axis
with 64 usteps per full step. These signals can be used to directly drive
each coil of the stepper motor for smooth, microstepped motion.
Encoder feedback is available for each motor axis and can be used by
the host to check that the axis has achieved a desired position.
Additionally, the chipset can use the encoder information to
automatically detect a motor stall condition while a move is ongoing.
The chipset calculates all trajectory information on a cycle-by-cycle
basis. Each cycle results in a new desired sine-wave frequency output
based on the trajectory generator mode and the specified trajectory
parameters.
The following table summarizes the operational parameters of the
MC1241-series chipsets.
17
MC1241-Series Chipset Operational Parameters
Available configurations:
Operating Modes:
Position Range:
Velocity Range:
Acceleration Range:
2 axes with internal microstepping generation (MC1241A)
1 axes with internal microstepping generation (MC1141A)
Open loop (motor is controlled directly by trajectory generator)
-1,073,741,824 to 1,073,741,823 usteps
-16,384 to 16,383 usteps/cycle with a resolution of 1/65,536 usteps/cycle
S-curve profile: - 1/2 to + 1/2 usteps/cycle2 with a resolution of 1/65,536 usteps/cycle2.
Jerk Range:
All others: -16,384 to 16,383 usteps/cycle2 with a resolution of 1/65,536 usteps/cycle2
-1/2 to +1/2 usteps/cycle3, with a resolution of 1/4,294,967,296 usteps/cycle3
Start velocity range
Trajectory Profile Generator Modes:
Electronic Gear Ratio Range:
Encoder Input Signals:
Microstepping Waveform:
# Steps Per Full Step:
Microstep Lookup Rate:
Phasing:
# of Output Phases:
PWM Frequency:
PWM resolution:
Max Incremental. Encoder Rate:
Profile Cycle Rate :
# of Limit Switch Inputs Per Axis
Miscellaneous control lines:
# of Position Capture Sources:
Capture Trigger Latency:
# of Host Commands:
-32,768 to +32,767 steps/cycle with a resolution of 1/65,536 steps/cycle
(used with trapezoidal and velocity profile modes only)
S-curve (host commands final position, max velocity, max acceleration, and jerk)
Trapezoidal (host commands final position, max velocity, starting velocity, and acceleration)
Velocity contouring (host commands max velocity, starting velocity, acceleration)
Electronic Gear (Encoder position is used as position command for corresponding axis).
32768:1 to 1:32768 (negative and positive direction)
A, B, Index
Sinusoidal
64
15 kHz
90 degrees (used with 2-phase stepper motors)
120 degrees (used with 3-phase stepper motors or AC Induction motors)
2 (all motor types)
97.6 kHz
8 bits
1.75 Mcounts/sec
540 uSec*.
2 (one for each direction of travel)
Home switch input (one per axis)
2 (Index, Home signals)
160 nSec
80
*Exact cycle time is 542.72 uSec, 540 is an approximation
Trajectory Profile Generation
The commands to select these profile modes are
The trajectory profile generator performs calculations to determine the
target position, velocity and acceleration on a continuous basis. These
calculations are performed taking into account the current profile mode,
as well as the current profile parameters set by the host. Four trajectory
profile modes are supported:
SET_PRFL_S_CRV (to select the s-curve mode), SET_PRFL_TRAP
(to select the trapezoidal mode) SET_PRFL_VEL (to select the
velocity contouring mode) and SET_PRFL_GEAR (to select the
electronic gear mod).
Throughout this manual various command mnemonics will be
shown to clarify chipset usage or provide specific examples. See
the Host Communications section for a description of host
command nomenclature.
- S-curve point to point
- Trapezoidal point to point
- Velocity contouring
- Electronic Gear
18
The profile mode may be programmed independently for each axis. For
example axis #1 may be in trapezoidal point to point mode while axis
#2 is in S-curve point to point.
Use the following figure showing a typical S-curve velocity vs. time
graph for reference in reading the next section:
Generally, the axis should be at rest when switching profile modes.
Under certain conditions however, switching into certain profile modes
"on-the-fly" is allowed. See specific profile descriptions for details.
Phase Phase Phase
I.
II.
III.
Phase
IV.
Phase Phase Phase
V.
VI.
VII.
S-curve Point to Point
The following table summarizes the host specified profile parameters
for the S-curve point to point profile mode:
Profile
Parameter
Destination
Position
Maximum
Velocity
Representation & Range
Units
signed 32 bits
-1,073,741,824 to 1,073,741,823
unsigned 32 bits* (1/216 scaling)
usteps
Max. Accel.
unsigned 16 bits ** (1/216 scaling)
0 to 32,767
unsigned 32 bits *** (1/232 scaling)
Jerk
S-curve profile
usteps/cycle
The S-curve profile drives the axis at the specified jerk until the
maximum acceleration is reached. (phase I). it will then drive the axis at
jerk = 0 (constant acceleration) through phase II. It will then drive the
axis at the negative of the specified jerk though phase III, such that the
axis reaches the specified maximum velocity with acceleration = 0. This
completes the acceleration phase. At the end of the acceleration phase
of the move, the velocity will be constant, and the acceleration will be 0.
At the appropriate time, the profile will then decelerate (phases V, VI
and VII) symmetrically to the acceleration phase such that it arrives at
the destination position with acceleration and velocity = 0.
0 to 1,073,741,823
usteps/cycle2
usteps/cycle3
0 to 2,147,483,647
* uses 1/216 scaling. Chipset expects a 32 bit number which
has been scaled by a factor of 65,536 from units of
usteps/cycle. For example to specify a velocity of 2.75
usteps/cycle, 2.75 is multiplied by 65,536 and the result is
sent to the chipset as a 32 bit integer (180,224 dec. or 2c000
hex.).
There are several conditions where the actual velocity graph of an Scurve motion will not contain all of the segments shown in the above
figure. For example, if the max. acceleration is not reached before the
"half-way" point to the max. velocity, then the actual velocity profile will
not contain a phase II or a phase VI segment (they will have a duration
of 0 cycles). Such a profile is shown below:
** uses 1/216 scaling. Chipset expects a 16 bit number which
has been scaled by a factor of 65,536 from units of
usteps/cycle2. For example to specify an acceleration of .175
usteps/cycle2, .175 is multiplied by 65,536 and the result is
sent to the chipset as a 16 bit integer (11,469 dec. or 2ccd
hex).
Phase
I.
Phase
III.
Phase
IV.
Phase
V.
Phase
VII.
*** uses 1/232 scaling. Chipset expects a 32 bit number which
has been scaled by a factor of 4,294,967,296 (232) from units
of usteps/cycle3. For example to specify a jerk value of .0075
usteps/cycle3, .0075 is multiplied by 4,294,967,296 and the
S-curve that doesn't reach max. acceleration
result is sent to the chipset as a 32 bit integer (32,212,256
dec. or 1eb8520 hex).
Another such condition is if the position is specified such that max.
velocity is not reached. In this case there will be no phase IV, and there
may also be no phase II and VI, depending on where the profile is
"truncated".
While the S-curve profile is in motion, the user is not allowed to
change any of the profile parameters. The axis must be at rest
before a new set of profile parameters can be executed. If
parameters are changed during motion then a 'command error'
19
will occur, and all new parameters will be ignored except the
position. See the section of this manual entitled "Command Error"
for more information..
The following figure shows a velocity profile for a typical point to point
trapezoidal move, along with a more complicated move involving on the
fly changes to the maximum velocity and the destination position.
Before switching to the S-curve point to point profile mode, the
axis should be at a complete rest.
Vel.
When the axis is in the S-curve profile mode, the SET_MAX_ACC
command should be used to load the max. acceleration value. The
alternate acceleration loading command SET_ACC can not be
used.
Time
Simple trapezoidal mode motion
Trapezoidal Point to Point
Vel.
The following table summarizes the host specified profile parameters
for the trapezoidal point to point profile mode:
Profile
Parameter
Destination
Position
Maximum
Velocity
Representation & Range
Starting
Velocity
unsigned 32 bits, (1/216 scaling)
0 to 1,073,741,823
unsigned 32 bits (1/216 scaling)
Accel.
change max
velocity
Time
Units
change destination
position
signed 32 bits
-1,073,741,824 to 1,073,741,823
unsigned 32 bits (1/216 scaling)
usteps
Complex trapezoidal mode motion
usteps/cycle
0 to 1,073,741,823
change destination
position
usteps/cycle
Vel.
usteps/cycle2
0 to1,073,741,823
starting
velocity
In the trapezoidal point to point profile mode the host specifies a
destination position, a maximum velocity, a starting velocity, and an
acceleration. The trajectory is executed by accelerating at the
commanded acceleration, beginning at the starting velocity, to the
maximum velocity where it coasts until decelerating such that the
destination position is reached with the axis at rest (zero velocity). If it is
not possible to reach the maximum velocity (because deceleration must
begin) then the velocity profile will have no "coasting" phase. The
acceleration rate is the same as the deceleration rate.
change max
velocity
Time
Trapezoidal Profile With Non-Zero Starting Velocity
Velocity Contouring
The following table summarizes the host specified profile parameters
for the Velocity contouring profile mode:
A new maximum velocity and destination position can be specified
while the axis is in motion. When this occurs the axis will accelerate or
decelerate toward the new destination position while attempting to
satisfy the new maximum velocity condition.
Profile
Parameter
Maximum
Velocity
Before switching to the Trapezoidal point to point profile mode,
the axis should be at rest.
Starting
Velocity
When in Trapezoidal point to point profile mode, to change the
acceleration, the axis must come to a complete stop. After this has
occurred, a new acceleration value can be loaded. If the
acceleration parameter is changed during motion then a
'command error' will occur, and all updated parameters will be
ignored except the position. See the section entitled 'Axis Status
for more informaton' on command errors.
Acceleration
Representation & Range
Units
unsigned 32 bits (1/216 scaling)
0 to 1,073,741,823
unsigned 32 bits, (1/216 scaling)
usteps/cycle
usteps/cycle
0 to 1,073,741,823
signed 32 bits* (1/216 scaling)
-1,073,741,824 to 1,073,741,823
usteps/cycle2
* negative numbers using 1/216 scaling are handled no
differently than positive numbers. For example if an
acceration value of -1.95 usteps/cycle2 is desired, -1.95 is
The Starting Velocity can not be changed while the axis is in
motion.
20
multipled by 65,536 and the result is sent to the chipset (127,795 dec. or fffe0ccd hex).
In this way the output of the microstep generator will precisely track the
input encoder position factored by a programmable gear ratio. This can
be useful in many applications where continuous synchronization with
an external mechanism is important.
In this profile mode the host specifies two parameters, the commanded
acceleration, and the maximum velocity. The trajectory is executed by
continuously accelerating the axis at the commanded rate until the max.
velocity is reached, or until a new acceleration command is given.
The following figure shows the arrangement for encoders and motor
drives in a typical electronic gearing application with the MC1241A
The maximum velocity value must always be positive. Motion
direction is controlled using the acceleration value. Positive
acceleration values result in positive motion, and negative values
result in negative motion.
Master
Encoder
Motor
The total number of geared axes supported per chipset is equal to the
number of motor axes. For each motor axes the encoder input for the
same axis is used as the master position command. In addition these
master/slave combinations are fixed, with the encoder for axis 1 driving
the axis 1 microstep generator, and the encoder for axis 2 driving the
axis 2 microstep generator.
The following figure shows a typical velocity profile using this mode.
Example Velocity Contouring Mode
change
acceleration
change
max velocity
Amplifier
Only one of four axes shown
There are no restrictions on changing the profile parameters on
the fly. Note that the motion is not bounded by position however.
It is the responsibility of the host to generate acceleration and
max. velocity command values which result in safe motion, within
acceptable position limits.
Vel.
MC1241A
Time
There are no restrictions on changing the gear ratio when the axis
is in motion, although care should be taken to select ratios such
that safe motion is maintained.
There are also no restrictions on changing to this profile mode
while the axes is in motion.
change max
velocity and
acceleration
There are no restrictions on switching the profile mode to velocity
contouring while the axis is in motion.
Trajectory Control
The Starting Velocity can not be changed while the axis is in
motion.
Normally each of the above trajectory modes will execute the specified
trajectory, within the specified parameter limits, until the profile
conditions are satisfied. For example for the point-to-point profile modes
this means that the profile will move the axis until the final destination
position has been reached, at which point the axis will have a velocity
of zero.
Electronic Gear
The following table summarizes the host specified profile parameters
for the electronic gear profile mode:
Profile
Parameter
Gear Ratio
Representation & Range
Units
signed 32 bits* (1/216 scaling)
-1,073,741,824 to +1,073,741,823
-
Halting The Trajectory
In some cases however it is necessary to halt the trajectory manually,
for safety reasons, or simply to achieve a particular desired profile. This
can be accomplished using one of two methods; abrupt stop, or smooth
stop.
* for example to specify a gear ratio of +1.5 to 1 the value
1.5*65,536 is sent to the chipset (98,304). Alternatively to set
the gear ratio as -11.39 to 1 the value -11.39*65,536 is sent (746,455 dec. or fff49c29 hex.).
Abrupt stops are accomplished using the STOP command. This
command instantaneously stops the trajectory generator by setting the
velocity of the axis to zero. This control mode is typically used during an
emergency stop, when no deceleration phase is desired.
In this profile mode, the host specifies one parameter, the gear ratio.
The target position is generated by applying the specified gear ratio to
the encoder position of the same axis, multiplying by the specified gear
ratio and outputting the corresponding number of microsteps.
Smooth stops are accomplished using the SMOOTH_STOP command.
This command causes the trajectory to decelerate at a rate equal to the
21
specified acceleration rate, until a velocity of zero is reached. In
addition the form of the deceleration is symmetric to the acceleration
phase. For example if the profile mode is S-curve, and a
SMOOTH_STOP command is given, the profile will decelerate in a
manner exactly equal and opposite to the acceleration phase.
Contouring profile modes only. They do not function when the
profile mode is set to electronic gearing.
The motion complete and in-motion bits indicate the state of the
trajectory generator, not the actual motor. Even if the trajectory
generator has completed a motion, the actual axis position may or
may not be at rest depending on motor stability, and other system
conditions.
The STOP command functions in all profile modes; S-curve pointto-point, Trajectory point-to-point, Velocity Contouring, and
Electronic Gear.
The SMOOTH_STOP functions in S-curve point-to-point,
Trajectory point-to-point, and Velocity Contouring profiling mode.
It does not function in Electronic Gear mode.
Parameter Loading & Updating
Various profile & motor control parameters must be specified by the
host for an axis to be controlled in the desired manner. To facilitate
precisely synchronized motion, these parameters and related control
commands are loaded into the chip using a double-buffered scheme. In
this scheme, the parameters and action commands being loaded are
not acted upon (copied from the double-buffered to the active registers)
until an update signal is given.
Caution should be exercised when using the STOP command due
to the large and abrupt changes in motion that may occur.
Motion Complete Status
To simplify the programming of a complete motion system it is
convenient to have the motion chipset indicate when a particular profile
move has been completed.
This update signal can consist of either a "manual" update command or
one of several conditional breakpoints. Whichever update method is
used, at the time the update occurs, all of the double buffered registers
and commands will be copied to the active registers. Conversely,
before the update occurs, loading the double-buffered registers or
executing the double buffered commands will have no effect on the
system behavior.
This function is provided by two status bits in the chipset's status word
(See the section of this manual entitled "Axis Status " for more
information on the axis status word). These two bits are called the
motion complete bit, and the in-motion bit.
The double buffered registers are listed below.
The motion complete bit is controlled interactively by the chipset and
the host. After a motion has completed, the chipset sets the motion
complete bit on. The host may then poll this bit to determine that motion
is complete, or if desired, the host can program the chipset to
automatically signal when the motion is complete (using an interrupt). In
either case once the host has recognized that the motion has been
completed the host clears the motion complete bit, enabling the bit to
indicate the end of motion for the next move.
Register Name
destination position
maximum velocity
acceleration
maximum acceleration
jerk
ratio
buffered motor command
The following list shows the conditions that will cause the motion
complete bit to occur:
-
Command to set
SET_POS
SET_VEL
SET_ACC
SET_MAX_ACC
SET_JERK
SET_RATIO
SET_BUF_MTR_CMD
The double-buffered commands are: STOP, SMOOTH_STOP, and
SYNCH_PRFL.
Profile has reached the destination position (point-to-point
profile modes only)
Axis trajectory reaches a velocity of zero and the current
velocity command is zero
SMOOTH_STOP command is given and axis trajectory
reaches a velocity of zero
STOP command is given
Limit switch condition occurs
Manual Update
There are two methods of manually updating the double-buffered
parameters & commands, one for a single axis instantaneous update
and one for a multiple-axis update.
The in-motion bit is similar to the motion complete bit except that it
continuously indicates the status of the axis without interaction with the
host. In addition this bit is used exclusively for polled mode operations.
It can not cause an interrupt to the host to be generated.
The single axis instantaneous update, which is specified using the
UPDATE command, forces the parameters for the current axis to be
updated at the next cycle.
The motion complete and the in-motion indicator bits function in
the S-curve point-to-point, Trapezoidal point-to-point, and Velocity
The multiple axis instantaneous update, which is specified using the
MULTI_UPDATE command, causes multiple axes to be updated
simultaneously. This can be useful when synchronized multi-axis
profiling is desired. This command takes a 1 word argument which
22
consists of a bit mask, with 1 bit assigned to each axis. Executing this
command has the same affect as instantaneously switching to each
desired axes, and executing an UPDATE command.
Motion Complete Breakpoint
A breakpoint can be specified which will result in the parameters
being updated when the previous motion has been completed
(motion complete bit is set). When using this breakpoint no 32 bit
compare value is required.
Breakpoints
External Breakpoint
A breakpoint can be specified which will result in the parameters
being updated when the home signal of the corresponding axis
becomes active (low). When using this breakpoint no 32 bit
compare value is required. This breakpoint is useful whenever it is
desired that an external signal starts, stops, or otherwise modifies
the profile movement.
A breakpoint is a convenient way of programming a profile or other
double-buffered parameter change upon some specific condition. There
are two types of breakpoints, those that have a 32-bit comparitor value
associated with them and those that do not. For those that have the
comparitor, a 32-bit comparitor value is loaded into the breakpoint
compare register first, and then one of the breakpoint conditions is
specified. For those breakpoint modes without associated comparitor
values only the breakpoint condition needs to be specified.
Normally, whenever one of these conditions has been programmed and
the condition occurs, the double-buffered parameters will automatically
be shifted to the active registers. There is a mechanism to disable this
"automatic update upon breakpoint" however. This is discussed in the
next section.
The double-buffered registers and commands will be updated upon
satisfaction of the specified breakpoint condition.
Here is a list of all of the available breakpoint conditions.
The above breakpoint modes are particularly useful during multi-axis
motion. This is because the next profile commands (set of hostspecified trajectory commands) can be pre-loaded and activated at the
precise position or time required, with no delay incurred to send an
update or load parameters command.
Positive Target Position Breakpoint
A 32 bit position breakpoint can be specified which will result in
the parameters being updated when the current target position
(the instantaneous desired axis position output from the profile
generator) equals or exceeds the specified breakpoint value. This
breakpoint is set using the SET_POS_BRK command.
After a breakpoint condition has been satisfied it is no longer
active. To set up another breakpoint condition, a new one must be
explicitly set by the host.
Negative Target Position Breakpoint
A 32 bit position breakpoint can be specified which will result in
the parameters being updated when the current target position
(the instantaneous desired axis position output from the profile
generator) equals or is less than the specified breakpoint
value.This breakpoint is set using the SET_NEG_BRK command.
The double-buffered registers that are shifted to the active
registers do not change upon being shifted, only the active
registers change.
Except for the MULTI_AXIS command, parameter loading and updating
is controlled individually for each axis. In addition each axis has a
separate 32-bit breakpoint register, and can be set to various individual
breakpoint conditions.
Positive Actual Position Breakpoint
A 32 bit position breakpoint can be specified which will result in
the parameters being updated when the current actual position
(the instantaneous position of the actual axis hardware) equals or
exceeds the specified breakpoint value.This breakpoint is set
using the SET_ACTL_POS_BRK command.
External Breakpoints and Homing
By connecting a home input sensor to the home signal input of the
MC1241-series chipsets it is possible to cause the chipset to halt a
motion at the moment it receives the home signal. This capability
makes it ideal for performing a home sequence. The following host I/O
sequence illustrates this:
Negative Actual Position Breakpoint
A 32 bit position breakpoint can be specified which will result in
the parameters being updated when the current actual position
(the instantaneous position of the actual axis hardware) equals or
is less than the specified breakpoint value.This breakpoint is set
using the SET_ACTL_NEG_BRK command.
GET_HOME
Time Breakpoint
A 32 bit time breakpoint can be specified which will result in the
parameters being updated when the # of cycles executed since
chip set reset (the current chip set time) is equal to the time
breakpoint value.The # of cycles continuously increases until it
rolls over from 232 - 1 back to 0.The time breakpoint is set using
SET_POS 12345
SET_VEL 23456
SET_ACC 345
UPDATE
SET_EXT_BRK
the SET_TIME_BRK command.
23
; check to make sure axis not already at
; home. If so, then a 'reverse' move must
; be made to retract axis from home switch.
; This ‘reversing’ sequence is not
; indicated here for simplicity sake
; load home move parameters
; start home move
; initiate external breakpoint mode
STOP
; load (but do not update) a stop command
2)
This sequence will start a homing move which will stop as soon as the
axis encounters the home switch.
Upon entering an over-travel condition, the trajectory generator
will automatically be halted, so that the motor does not travel
further into the over travel region.
To recover from an over-travel condition the corresponding status bits
in the status word should be reset (see the section of this manual on
axis status for details on resetting status word bits). Once this has been
performed the host can command a trajectory move to bring the axis
out of the over-travel region.
As is the case for all of the breakpoint modes, the external breakpoint
can not only be use to stop an ongoing move, but to start or otherwise
modify a move as well. This flexibility makes it well suited for
applications such as cut-on-the-fly where externally-initiated motions
are required.
The over-travel detector is 're-armed' when the axis exits the over travel
condition.
Disabling Automatic Profile Update
Only one over-travel signal can be processed at a time. For
example if the negative over travel switch becomes active, the
corresponding status bits must be cleared, and the axis moved
into the legal travel range before a positive over travel switch will
be recognized.
Normally, when a breakpoint condition has been satisfied, it causes the
profile and other double-buffered parameters to be automatically
updated. For certain types of profiles however, it may be desirable to
still use the breakpoint mechanism (to allow it to generate a host
interrupt for example), but not to have the profile update.
Axis Timing
Whether the profiles are automatically updated or not for a given axis is
controlled by the commands SET_AUTO_UPDATE_ON and
SET_AUTO_UPDATE_OFF. When auto update is set to on, the
breakpoint/profile mechanism behaves as described above. When set
to off, upon a breakpoint condition, no profile update will occur. When in
this mode the only way to update the profile is to use the UPDATE
command or the MULTI_UPDATE command.
Each axis of the MC1241-series chipsets receives a "time slice" of the
available computation power of the CP chip. The amount of time
required for the chipset to perform one complete pass of calculations for
all of the axes is known as the chipset cycle time. This chipset cycle
time is important to the host processor because it determines the rate at
which profile trajectories are updated.
The cycle time is the same for all MC1241-series chipsets. The cycle
time value is 540 uSec*. All velocities, accelerations, and jerk values
are related to this cycle time via the various trajectory generator modes
that generate axis motion.
Travel Limit Switches
The MC1241-series chipsets support motion travel limit switches that
can be used to automatically recognize an "end of travel" condition.
* exact cycle time is 542.72 uSec, 540 is an approximation.
The following figure shows a schematic representation of an axis with
travel-limit switches installed, indicating the "legal" motion area and the
over-travel regions.
negative limit
switch
negative
over-travel
region
For example, to determine the velocity of a given axis in units of
steps/second, we use the conversion ration 1 sec = 1,851 cycles (1,851
cycles/sec = 1 cycle every 540 uSec). Therefore if the desired
maximum velocity to be provided to the chipset is (for example) 12,345
usteps/sec we convert to units of usteps/cycle by dividing by 1,851,
giving a value of 6.669. The value we send to the chipset using the
SET_VEL command (see host command section for details) would be
65,536 times this amount since the velocity parameter uses 1/2 16
positive limit
switch
scaling. Therefore we would send a value of 437,083 to the chipset.
Legal travel region
positive
over-travel
region
As an additional example, to determine the acceleration of a given axis
in units of usteps/second2, we again use the conversion ration 1 sec =
1,851 cycles, however we must take into account the conversion to
cycles2 (not cycles). Therefore if the desired acceleration to be
There are two primary services that the MC1241A provides in
connection with the over-travel limit switch inputs:
1)
provided to the chipset is (for example) 67,890 usteps/sec2 we convert
to units of usteps/cycle2 by dividing by 1,8512 (or 3,426,201), giving a
The host can be automatically notified that an axis has entered
an over-travel condition, allowing the host to take appropriate
special action to manage the over-travel condition.
value of .0019815. The value we send to the chipset using the
SET_ACC command (or SET_MAX_ACC command if we are in Scurve mode) would be 65,536 times this amount since this parameter
24
uses 1/216 scaling. Therefore we would send a value of 1298 (decimal)
to the chipset.
signal is then brought high to end the transfer of the first byte. To
transfer the second (low) byte, ~HostSlct, ~HostRead, and ~HostCmd
are again brought low and the data should be read from the data bus.
All MC1241-series chips have the same cycle time (540 uSec),
which is not adjustable by the host.
Before any command write, data write or data read operations are
performed, the user must check that the HostRdy signal indicates
ready. After a command write, or after the second byte of each
read or write, this signal will go busy. It will return to ready when
the chipset can receive another I/O operation.
Host Communications
Electrical Interface
For more specific electrical information on the host interface operations,
see the pin descriptions and the timing diagram.
The MC1241A communicates to the host processor via an 8-bit bidirectional data port. 5* additional signals are used to synchronize
communication operations. The following table gives a brief description
of the control signals used during host communication:
Packet Format
Signal
~HostSlct
~HostWrite
~HostRead
HostCmd
HostRdy
All communications to/from the chip set take the form of packets. A
packet is a sequence of transfers to/from the host resulting in a chip set
action or data transfer. Packets can consist of a command with no data
(Dataless Command), a command with associated data that is written
to the chip set (Write Command) or a command with associated data
that is read from the chip set (Read Command).
Description
Selects the host port for operations
Writes a byte of data (or a command) to the chip
set. A write operation can only occur when the
ready/busy line indicates ready
Reads a byte of data from the chip set. A read
operation can only occur when the ready/busy line
indicates ready
Is asserted in combination with the HostWrite signal
when a command is being written to the chip set.
Indicates to the host that the host port is available
for operations
All commands with associated data (read or write) have either 1 or 2
words of data. See the host commands section for more information on
the length of specific commands.
If a read or a write command has 2 words of associated data (a 32 bit
quantity) the high word is loaded/read first, and the low word is
loaded/read second.
*An additional signal, HostIntrpt is provided to the host. This
signal is not used directly in communication operations, and is
discussed in a separate section
The following charts show the generic command packet sequence for a
Dataless Command, a Write Command, and a Read Command. The
hardware communication operation described in the previous section to
accomplish each type of transfer is shown in the left column.
Three types of hardware communication operations are possible
between the host processor and the chip set; Command Write, Data
Write and Data Read. Each of these operations transfers information to
or from the chip set, and is coordinated using the 5 control signals listed
above.
Dataless Command
Time
A Command Write operation involves the transfer of a single byte
command to the chip set. To perform a write command operation, the
desired command is loaded on the 8 data pins and ~HostSlct and
~HostWrite are brought low, while HostCmd is brought high.
Cmd Write:
Data Write:
Data Read:
-->
-->
-->
-->
Cmd byte
[pkt checksum]
Write Command
A Data Write operation involves the transfer of two bytes of data (1
word) to the chip set. To transfer the first byte (high byte), the desired
data byte is loaded on the 8 data bits and ~HostSlct, ~HostWrite and
HostCmd are brought low. The HostWrite signal is then brought high to
end the transfer of the first byte. To transfer the second byte (low byte),
the desired data byte is loaded on the 8 data bits and ~HostSlct,
~HostWrite and HostCmd are again brought low.
Time
Cmd Write:
Data Write:
Data Read:
A Data Read operation involves the transfer of two bytes of data (1
word) from the chip set to the host. To transfer the first (high) byte,
~HostSlct, ~HostRead,and ~HostCmd signals should be brought low,
and the data should be read from the 8 bit data bus. The HostRead
25
-->
-->
-->
-->
Cmd byte
word 1 [word 2]
[pkt checksum]
Command Errors
Read Command
Time
-->
Cmd Write:
Data Write:
Data Read:
-->
-->
If a command, or command sequence is sent to the chipset that is not
valid at a given operating condition of the chipset, but is valid at other
times, this command is said to cause a command error.
->
Cmd byte
When a command error occurs this condition is indicated by the
'command error' bit of the axis status word (See the section of this
manual entitled "Axis Status" for more information on the axis status
word).
Word 1 [Word 2] [pkt checksum]
[ ] Indicates an optional operation
The following list indicates the command sequences that result in a
command error:
Packet Checksum
The above charts show that at the end of each packet, a checksum
word is available for reading.
-
Although host to chip set I/O operations are extremely reliable, for
critical applications the checksum can provide a further reliability
enhancement (particularly in very noisy electrical environments, or
when the communication signals are routed over a media that may
have data losses such as a serial link).
Changing and updating the acceleration (SET_ACC, UPDATE)
when in the trapezoidal profile mode and when the axis
trajectory is still in motion.
-
Changing and updating either the velocity, max acceleration, or
jerk (SET_VEL or SET_MAX_ACC or SET_JERK, and then
UPDATE) when in the S-curve profiling mode and when the
trajectory is in motion
-
Commanding a move in the same direction as a limit switch
condition when in Trapezoidal or S-curve profile mode. For
example if travelling in the positive direction and a limit switch
is encountered, a further move in the positive direction will be
ignored and a command error will be generated.
This checksum consists of a 16-bit sum of all previous communications
that have occurred for the associated command. The command byte is
included in the low byte of the 1st checksum word (high byte set to 0).
Data words are added as is to the checksum value.
For example if a SET_VEL command (which takes two 16-bit words of
data) was sent with a data value of fedcba98 (hex), the checksum
would be:
Once a command error occurs the command error bit is set, and the
illegal profile changes are ignored. If additional parameters are also
changed such as position or any filter values as part of the same
UPDATE command then these parameters will not be rejected at the
time of the UPDATE, and they will become the active values.
0011
(code for SET_VEL command)
+ fedc
(high data word)
+ ba98 (low data word)
---------1b985
check sum = b985 (keep bottom 16 bits only)
Axis Addressing
Most chip set commands alter the parameters or the operating state of
one axis at a time. In this way each axis can be controlled separately.
To facilitate efficient communication for these types of commands, the
chip set maintains the concept of a current axis number, which can be
set explicitly by the host. After setting the current axis number,
commands that are addressed to the current axis will automatically
operate on this axis. The current axis number will stay the same until it
is changed by one of the commands that alter the current axis number.
Reading the checksum is optional. Recovering from an incorrect packet
transfer (bad checksum) will depend on the nature of the packet. Read
and Write operations can always be re-transmitted, while a command
resulting in an action may or may not be re-tried, depending on the
command and the state of the axis.
Illegal Commands
As an illustration of this, the following sequence sets the current axis to
#2, updates some motion parameters, and switches to axis #1, and
alters some other motion parameters.
When the MC1241A receives a command that is illegal (see host
command summary for listing of illegal commands), it will signal this
condition by returning a checksum of 0, regardless of the illegal
command value or the value of any subsequent data written to the host
as part of the illegal command sequence.
SET_2
SET_POS
In this manner the host processor checksum can be used to detect
communication problems as well as an illegal command sequence,
resulting in a simplification of the host processor communication code.
UPDATE
26
02345678
-> sets current axis to #2
-> loads current axis (#2) dest.
position with value of 2345678
-> causes the loaded value to take
effect (axis # 2)
SET_1
SET_ACCEL
00001234
UPDATE
-> sets current axis to #1
-> loads current axis (#1) with
acceleration value 1234
-> causes the loaded value to take
effect (axis # 1)
Bits 0-7 indicate various status flags that can also generate host
interrupts (see next section for details). These flags are set by the
chipset, and must be reset by the host (They will not be cleared by the
chipset).
Bits 0-7 of the status word operate using a set/reset mechanism.
These flags are set by the chipset, and must be reset by the host.
If they are not reset by the host they will remain active indefinitely.
Axis Status
The MC1241A supports a status word for each axis, which contains
various information about the state of the axis.
Miscellaneous Mode Status Word
The status word is a 16-bit register which can be queried using the
command GET_STATUS. It contains the following information (Bit
encoding is 0 = LSB, 15 = MSB):
Bit #
0
1
2
3
4
5
6
7
8
9
10
11
12,13
14,15
There is another status word available that indicates the current status
of various mode settings or conditions.
Description
Motion complete flag. This bit is set (1) when the axis
trajectory has completed. This flag is only valid for the Scurve and trapezoidal, and velocity contouring profile
modes.
Wrap-around condition flag. This bit is set (1) when the axis
has reached the end of its travel range,and has wrapped to
the other end of the travel range. Specifically, when
travelling in a positive direction past the position
+1,073,741,823, the axis will wrap to position 1,073,741,824, and vice-versa.
Breakpoint reached flag. This bit is set (1) when one of the
breakpoint conditions has occurred.
Index pulse received flag. This bit is set (1) when an index
pulse has been received.
Motion error flag. This bit is set (1) when the position error is
exceeded (see filter section for more information). This bit
can only be reset when the axis is no longer in a motion
error condition
Positive limit switch flag. This bit is set (1) when the positive
limit switch goes active.
Negative limit switch flag. This bit is set (1) when the
negative limit switch goes active.
Command error flag. This bit is set (1) when a command
error has occurred.
motor on/off status (1 indicates motor is on, 0 indicates
motor is off).
axis on/off status (1 indicates on, 0 indicates off).
In-motion flag. This bit continuously indicates whether or not
the axis trajectory is in motion. This bit is set (1) when the
axis is in motion, and cleared (0) when the axis trajectory is
not in motion.
reserved (may contain 0 or 1)
current axis # (13 bit = high bit, 12 bit = low bit). Therefore
axis encoding is as follows:
Bit 13
Bit12
Axis
0
0
1
0
1
2
reserved (may contain 0 or 1)
The miscellaneous mode status word is a 16-bit register which can be
queried using the command GET_MODE. It contains the following
information (Bit encoding is 0 = LSB, 15 = MSB):
Bit #
0-6
7
8-9
10
11,12
13-15
Description
Used internally by chipset. Contains no host-useable
information.
Stop on motion error mode flag. This bit indicates the state
of the stop on motion error mode, set by the commands
SET_AUTO_STOP_ON and SET_AUTO_STOP_OFF. A 1
indicates auto stop is on.
Used internally by chipset. Contains no host-useable
information.
Auto update flag. This bit indicates the state of the auto
update mode, set using the commands
SET_AUTO_UPDATE_ON and
SET_AUTO_UPDATE_OFF. A 1 indicates that auto update
is disabled.
Trajectory generator mode. This bit indicates the mode of
the trajectory generator, set using the commands
SET_PRFL_S_CRV, SET_PRFL_TRAP, SET_PRFL_VEL,
SET_PRFL_GEAR. The encoding is as follows:
Bit 12
Bit11
Profile Mode
0
0
trapezoidal
0
1
velocity contouring
1
0
s-curve
1
1
electronic gear
Phase #. These bits indicate the current phase # of the Scurve profile (only valid if the current profile mode is Scurve). A 0 indicates that the profile has not started yet, and
phases 1-7 indicate the phase #'s corresponding to the
phases described in the S-curve profiling mode. The 3-bit
phase # word is encoded bit 15 MSB, and bit 13 LSB.
Host Interrupts
In many situations, during axis motion or at other times, it is useful to
have the chip set signal the host that a special condition has occurred.
This is generally more convenient and efficient than having the host poll
Bits 8-10 and 12-13 indicate continuous status information, and do not
need to be reset by the host.
27
the chip set for various possible conditions. This chip set-initiated signal
is known as a host interrupt.
Several chip set conditions may occur that can result in the generation
of a host interrupt. Whether these conditions in fact interrupt the host is
controllable for each condition and for each axis. The mechanism used
to control each condition is a mask register.
SET_INTRPT_MASK
Sets the interrupt conditions mask
GET_INTRPT
Returns the status of the interrupting axis
(including the interrupting axis #). The
current axis # is not altered by this
command
Changes the current axis # to the
interrupting axis. This is a 'time saver'
command which performs the dual
operations of getting the interrupting axis
# and switching to that axis in one
command.
Clears particular conditions for the
interrupting axis. The current axis # is not
altered by this command.
SET_I
The interrupt conditions correspond to bits 0-7 and 11 of the
status register (the axis event flags), described in the previous
section. These conditions are summarized below:
Motion Complete
Wrap-around condition
Break Point Reached
Position Capture
Received
Motion Error
Negative Limit Switch
Positive Limit Switch
Command Error
Occurs when the profile is complete
Occurs when the axis position wraps.
Occurs when a breakpoint condition has
been satisfied.
Occurs when the encoder index pulse or
home pulse has been captured
Occurs when the maximum position
error set for a particular axis has been
exceeded
Occurs when the negative over-travel
limit switch is active
Occurs when the positive over travel
limit switch is active
Occurs when a host communication
sequence causes a command error
condition
RST_INTRPT
To facilitate determining the nature of the interrupt, the status register
holds the axis #, allowing the interrupting axis # to be determined.
The following represents a typical sequence of interrupt conditions and
host responses. Assume for the purposes of this example that an axis
(not the current axis) has hit a "hard stop" causing an essentially
instantaneous motion error, as well as a positive limit switch trip. Also
assume that the interrupt mask for this axis was set so that either
motion errors or limit switch trips will cause an interrupt
Event
motion Error & limit switch trip
generates interrupt
interrupting axis status
returned by chipset, current
axis set to interrupting axis.
When one of these interrupt conditions occur for a particular axis, the
host interrupt line is made active. At this point the host can respond to
the interrupt (although the current I/O operation should be completed),
but it is not required to do so
When the host has completed processing the interrupt, it sends a
command that clears the interrupt conditions for a particular axis, the
RST_INTRPT command.
chipset clears motion error bit
and disables host interrupt line
Because limit switch interrupt
is still active chipset
immediately generates
interrupt for limit switch
interrupting axis status
returned by chipset, current
axis set to interrupting axis.
This command includes a "clearing mask" as an argument, which
allows one interrupt to be cleared at a time.
Bits cleared by the RST_INTRPT command are the exact same bits
as those cleared by non-interrupt commands such as
RST_STATUS and CLR_STATUS. In each case the bits affected are
the status word bits 0-7.
Interrupts occur for a particular axis. If the user is currently
programming parameters on axis #1 and an interrupt occurs on axis #2,
it is the host's responsibility to change axis number to 2 if this is the
appropriate response to an interrupt on that axis. If more than one axis
interrupt condition becomes active at exactly the same time, then the
axis with the lowest number will generate the interrupt first.
chipset clears limit switch bit
and disables host interrupt line
Host action
host sends SET_I command
host detects motion error & limit
switch flags are set, recovers from
motion error first.
host sends: RST_INTRPT 00EF,
clearing motion error bit
host sends SET_I command
host detects that neg. limit switch
trip flag is set, performs recovery
for limit switch trip.
host sends RST_INTRPT 00DF,
clearing pos. limit switch bit
-
At the end of this sequence, all status bits are clear, the interrupt line is
inactive, and no interrupts are pending.
The following host commands are used in managing interrupts:
(See Host Command reference for complete information)
Note that it is not required to process multiple interrupts separately (as
is shown in the example). It is perfectly valid to process 2 or more
interrupt conditions at the same time, and to then send a RST_INTRPT
command with a mask that clears multiple bits at the same time.
28
The RST_INTRPT and GET_I commands are only effective when
there is an interrupt present. If no interrupt is present than
alternative 'polled-mode' commands such as RST_STATUS or
GET_STATUS should be used.
High Speed Position Capture
Encoder Position Feedback
Two separate trigger signals are available, although there is only one
capture register. The trigger signal source is selected by the host and
can be either the index signal, or the home signal. Selection of the
index input or the home input as the trigger source is made using the
SET_CAPT_INDEX and SET_CAPT_HOME commands.
Each axis of the MC1241A supports a high speed encoder position
capture register that allows the current 32-bit axis location to be saved
based on an external trigger signal.
The MC1241A-series of chipsets support direct input of incremental
encoder signals. Four position input and control signals are supported:
- A quadrature channel
- B quadrature channel
- Index pulse
- Home signal
Position Capture Readback
After a triggering signal has caused a position capture in the MC1241A
the stored position may be read by the host processor. The axis status
word indicates whether or not a capture has occurred. The command
GET_CAPT is used to retrieve the position stored at the time of the
home signal trigger.
The A and B signals are used to continuously maintain the position of
the motor, and the index and home signals are used as trigger inputs to
a high-speed position capture mechanism.
Each quadrature channel consists of a square wave offset 90 deg. from
the other. Positive motion consists of the A channel leading the B
channel by 90 deg., and negative motion consists of the A channel
lagging the B channel by 90 deg. For each full phase of one channel,
four resolved quadrature counts will occur, resulting in a 4 to 1
resolution enhancement over the basic channel resolution.
The captured position is equal to the axis position at the moment the
trigger pulse was encountered (including other required signal states
defined above). Note that the capture register is located in hardware. Its
accuracy is therefore not affected by the velocity of the axis.
The position captured by the high-speed position capture register
is the actual axis position of the motor encoder, not the trajectory
generator position.
The index pulse is typically located on the encoder and will be active
once per revolution. The chip set recognizes that an index trigger has
occurred (i.e. when the 32-bit index location is captured) when the
index signal, as well as the A and B signals transition low.
To read a sequence of positions the capture value must be read
by the host processor before another position capture can occur.
For example if a trigger occurs, and a second trigger occurs
before the capture position was read using the GET_CAPT
command, no capture will occur from the second triggering
signal.
The home signal is typically connected to a position reference sensor,
or to any other general purpose synchronizing signal. The home signal
is recognized when it alone transitions low. The state of the A and B
signals does not affect home signal trigger recognition.
Stall Detection
Encoder Filtering
The MC1241A chipset supports two primary operations in connection
with encoder feedback:
To enhance reliability of the received encoder information the MC1241A
provides digital filtering of the quadrature data lines (A and B
quadrature count) as well as the index and home signals.
- readback of current axis position
- automatic stall detection.
For all of these signals a valid high or low condition is recognized only
when the condition has been maintained for 3 clock cycles of 160 nSec
each (total required duration of 480 nSec)
Readback of the current encoder position is accomplished using the
GET_ACTL_POS command. This command allows the user to confirm
that the stepper axis has achieved a particular location. The
GET_ACTL_POS command can be used at any time, whether the axis
is in motion or not.
For example if a brief spurious noise signal on one of the lines occurs
for 300 nSec, then this noise will be rejected until a valid state change
lasting over 480nSec occurs.
Automatic stall detection allows the chipset to detect when the step
motor has lost steps during a motion. This typically occurs when the
motor encounters an obstruction, or otherwise exceeds its rated torque
specification.
29
Automatic stall detection operates continuously once it is initiated. The
current desired position (target position) is compared with the actual
position (from the encoder) and if the difference between these two
values exceeds a specified limit a stall condition is detected.
If the automatic motor stop mode is not set than only the motion error
status bit is set.
Recovering From A Motion Error
To initiate automatic stall detection the host must specify the number of
encoder counts per output micro step. This is accomplished using the
command SET_STEP_RATIO. The following equation shows how this
value should be set for various values of encoder count resolution.
To recover from a motion error which results in the microstep output
being halted, the following sequence should be performed:
Ratio = (Ncounts/Npulses)*256.
where:
Ratio is the ratio value specified to the SET_STEP_RATIO
command
Ncounts is the number of encoder counts per motor
1)
Determine cause of motion error and correct problem (this may
require human intervention).
2)
Re-enable motor output using the MTR_ON command
After the above sequence the axis will be at rest, and the position error
between the target position and the actual encoder position will be set
to zero.
rotation.
Npulses is the number of output micro steps per motor
rotation. This value 12,800 for a 1.8 degree step motor
and 3,200 for a 7.2 degree step motor
Resetting the position error is useful not only for motion error recovery
but also when the coordinate system is changed. Several commands
reset the position error to zero. These commands are
SET_ACTL_POS, which sets the actual as well as the target position to
a particular value, and SYNCH_PRFL, which sets the actual position
equal to the target position. The SYNCH_PRFL command will not take
affect until an UPDATE command is given.
For example if a step motor with 1.8 degree full step size is used with
an encoder which has 4,000 counts per motor rotation, the ratio
specified in the SET_STEP_RATIO command would be
(4,000/12,800)*256, or 80.
Although the MC1241A supports stall detection with encoders that have
a different number of counts then pulses, the ratio provided with the
SET_STEP_RATIO command must be an exact integer. For example
in the above example an encoder with 4,000 counts per rotation which
gives a ratio value of 80 is acceptable however an encoder with 4,096
which gives a ratio value of 81.92 is not acceptable.
Microstepping
In addition to trajectory generation the MC1241A chipset provides direct
internal generation of microstepping signals for 2-phase as well as 3phase stepper motors.
The following diagram shows an overview of the control flow of the
microstepping scheme:
Position Error
The difference between the desired position, also called the target
position, and the actual encoder position is known as the position error,
or the actual position error.
Motor Output
(PWM or DAC16)
Motor command register
(SET_MTR_CMD)
The position error is continuously maintained by the chipset and can be
read by the host at any time. To read the position error the command
GET_ACTL_POS_ERR is used.
Phase A
command
Phase B
command
To perform the stall detection function the position error is continuously
compared with the maximum allowed position error, which is set using
the command SET_POS_ERR. To read this value back the command
GET_POS_ERR is used. The units of the maximum position error is
encoder counts.
To
Amp.
Trajectory
Generator
If the maximum position error value is exceeded (stall is detected), then
the axis is said to be in a "motion error" condition. When this occurs the
motion error bit in the axis status word is set, and further pulse
generation may be halted, depending on the state of the automatic
motor shutdown mode (see SET_AUTO_STOP_ON and
SET_AUTO_STOP_OFF host command descriptions).
The microstepping portion of the chipset generates a sinusoidal
waveform with 64 distinct output values per full step (one full step = a
quarter electrical cycle).
The output frequency of the microstepping signals are controlled by the
trajectory generator. The amplitude of the microstepping signals are
controlled using a register that can be set by the host processor known
30
as the motor command register. Adjustment of this register by the host
allows different motor power levels during (for example) motion, and at
rest.
For 3-phase stepper motors or AC Induction motors, the phase C
waveform must be constructed externally using the expression C = (A+B). Typically this is performed by the motor amplifier itself. See the
following section of this manual entitled "Motor Output" for more
information.
Two microstepping waveforms are provided, one appropriate for
traditional 2-phase stepper motors with 90 deg. of separation between
phases, and one appropriate for 3-phase stepper motors and AC
Induction motors with 120 deg. separation between phases. For more
information on AC Induction Motor Control see the section entitled AC
Induction Motor Control.
Motor Command Control
The MC1241A provides the ability to set the motor command (power
output) level of the stepper motor. This is often useful to optimize the
motor torque, power consumption, and heat generation of the motor
while it is at rest, or in various states of motion.
Microstepping Waveforms
The motor output level is controlled by the motor command register.
This register can be set using one of two commands; SET_MTR_CMD
and SET_BUF_MTR_CMD. These commands are identical except that
SET_BUF_MTR_CMD is double buffered, and requires an UPDATE or
a breakpoint to occur before it takes effect. This feature can be used to
advantage when it is desired that the motor power changes be
synchronized with other profile changes such as at the start or the end
of a move.
To specify 2-phase motor waveforms use the command
SET_PHASE_2, and to specify 3-phase motor waveforms use the
command SET_PHASE_3.
Regardless of the waveform selected or the motor output signal format
(PWM or DAC16), 2 output signals per axis will be provided by the
chipset. The following chart shows this.
Waveform
Motor Output Mode
2-phase
2-phase
3-phase
3-phase
PWM
DAC16
PWM
DAC16
# of Output signals
& Name
2 (A, B)
2 (A, B)
2 (A, B)
2 (A, B)
Changing the power level does not affect the microstepping
output phasing or the frequency of the output waveform, it simply
adjusts the magnitude of the waveform.
AC Induction Motor Control
For specific pin assignments of the PWM and DAC16 motor output
signals see the section of this manual entitled 'Pin Descriptions'.
The MC1241A chipset can be used as the basis of a variable speed 3phase AC Induction motor controller. In this mode the chipset is set for
a 3-phase waveform, and is operated as if it were a stepper motor. The
position of the motor is not precisely maintained, however the velocity
of the AC Induction motor can typically be controlled to within 10 - 20
percent.
The diagram below shows the phase A, B signals for a 2-phase stepper
motor, and the phase A, B signals for a 3-phase stepper motor or AC
Induction motor.
Such a controller can be used for spindles, and other motors where
velocity control, not positioning is required.
2-Phase Stepper
Phase A
Phase B
When running an AC Induction motor using variable speed control care
should be taken that the output drive signal should never have a
frequency of 0. Even if the motor is not rotating the drive frequency
should have at least some rotational frequency. This is because a
relative difference in the frequency of the drive signals and the motor
rotor (called the slip frequency) is required to avoid magnetic field
saturation at rest, a potentially damaging condition.
90 Deg
Microsteps
64
128
192
256
320
Using the MC1241A up to two AC Induction motors can be controlled,
and using the MC1141A one can be controlled. The output drive
configuration is the same as for 3-phase steppers shown in the 'Motor
Output Configuration' section below.
3-Phase Stepper
Phase A
Phase B
Phase C
The MC1241A chipset does not provide 'Flux Vector Control' of AC
Induction Motors, only variable speed control. Therefore the
MC1241A should not be used in AC Induction applications
involving precision positioning.
120 Deg
31
Command Summary:
DAC16 Decoding
The following table summarizes the commands that are used in
conjunction with microstepping signal generation:
Command
Function
SET_PHASE_3
Sets the commutation waveform for 3phase brushless motors.
SET_PHASE_2
Sets the commutation waveform for 2phase brushless motors.
GET_PHASE_INFO
Returns type of waveform selected.
SET_MTR_CMD
Sets the motor command register, used
to control the motor output amplitude.
SET_BUF_MTR_CMD
Sets the buffered motor command
register. Functions identically to
SET_MTR_CMD except that an
UPDATE is required for it take effect.
The digital values output by the chipset to the DAC encode the desired
voltages as a 16-bit digital word. The minimum voltage is output as a
digital word value of 0, a voltage of 0 Volts is output as a digital word of
32,768 (dec.), and the maximum positive voltage is output as a digital
word value of 65,535 (dec.).
To load each of the four (MC1241A) or two (MC1141A) DACs, the DAC
control pins in combination with the chipset's 16-bit data bus are used.
To load a particular DAC, The DAC address (1 of 4) is output on the
signals DAC16Addr0-1, the 16 bits of DAC data are output on pins
Data0-11 (high 12 bits), as well as DACLow0-3 (low 4 bits), I/OAddr0-3
and DACSlct are high, and I/OWrite is low.
For more information on the DAC signal timing & conditions, see the
Pin Descriptions and timing diagrams section of this manual.
DACs with lower resolution than 16 bits can also be used. To connect
to a DAC with less resolution, the high order bits of the 16-bit data word
should be used. For example, to connect to an 8-bit DAC, bits Data4Data11 should be used. The low order 8 bits are written to by the
chipset, but ignored by the DAC circuitry.
Motor Output
The MC1241A series of chipsets support two motor output methods,
PWM and DAC.
The motor output method is host-selectable. The selected method
affects all axes (motor output mode is not individually programmable for
each axis). The host commands to select these output modes are
SET_OUTPUT_PWM (to select PWM mode), and
SET_OUTPUT_DAC16 (to select 16 bit DAC mode).
PWM Decoding
The PWM output mode also outputs a sinusoidal desired voltage
waveform for each phase, however the method by which these signals
encode the voltage differ substantially from the DAC16 digital word.
The PWM output mode uses a magnitude signal and a sign signal. The
magnitude signal encodes the absolute value of the output sinusoid and
the sign signal encodes the polarity of the output, positive or negative.
The following diagram shows the magnitude and sign signals for a
single output phase.
Motor Output Signal Interpretation
The diagram below shows typical waveforms for a single output phase
of the MC1241A chipset. Each phase has a similar waveform, although
the phase of the B channel output is shifted relative to the A channel
output by 90 or 120 degrees (depending on the waveform selected).
PWM Magnitude
(low pass filtered)
+ motor command
+5 V
0V
0
- motor command
PWM Sign
+5 V
The waveform is centered around an output value of 0. The magnitude
of the overall generated waveform is controlled by the motor command
register (SET_MTR_CMD or SET_BUF_MTR_CMD cmds).
0V
In this diagram the PWM magnitude signal has been filtered to convert
it from a digital variable duty cycle waveform to an analog signal.
For example if the chipset is connected to a DAC with an output range
of -10 Volts to + 10 Volts and the chipset is set to a motor command
value of 32,767 (which is the maximum allowed value) than as the
motor rotates through a full electrical cycle, a sinusoidal waveform
centered at 0 volts will be output with a minimum voltage of - 10, and a
maximum voltage of +10.
Before filtering this signal contains a pulse-width encoded
representation of the 'analog' desired voltage. In this encoding the duty
cycle of the waveform determines the desired voltage. The PWM cycle
has a frequency of 97.6 kHz, with a resolution of 8 bits, or 1/256.
The following chart shows the encoding.
32
Several single-chip amplifiers are available which are compatible with
these input signals. These amplifiers require an analog reference input
(low-passed PMWMag signal from chipset) as well as a sign bit
(PWMSign signal from chipset). The amplifier in-turn performs current
control typically using a fixed-off time PWM drive scheme (See
application notes section of this document for an example of such a
circuit)
0/256
1
(min. value)
0
1
128/256
(50 % value) 0
The diagram below shows this amplifier scheme:
255/256 1
(max. value)
0
Amplifier
An output pulse width of 0 parts per 256 represents the minimum
voltage, an output pulse width of 128 per 256 (50 %) represents a
voltage of 50 % total scale and a pulse width of 256 per 256 represents
the maximum positive voltage.
PWM Mag. A
Low Pass
Filter
PWM Sign A
Motor
MC1241A
PWM Mag. B
PWM Sign B
Low Pass
Filter
Motor Drive Configurations
Below is shown a typical amplifier configuration for a 2-phase stepper
motor using either the PWM or DAC output mode.
Current
Control
H-Bridge
Relative to the DAC output method the PWM output mode when used
with this amplifier scheme has the advantage of high performance with
a minimum of external parts. This amplifier scheme is shown below for
a single motor axis (two phases).
2-Phase Motor Output Connection Scheme
Amplifiers
Axis #1 phase A
3-Phase Drive Configuration
Mtr #1
Axis #1 Phase B
Below is shown a typical amplifier configuration using the MC1241A in
DAC mode for a 3-phase stepper or for an AC Induction motor with 3
phases.
MC1241A
Axis #2 phase A
Current
Control
H-Bridge
Mtr #2
3-Phase Motor Output Connection Scheme
Axis #2 Phase B
Amplifiers
Using the DAC output mode the digital motor output word for each
phase is typically converted into a DC signal with a value between -10
to +10 volts. This signal can then be input into an off-the-shelf DCServo type amplifier (one amplifier for each phase) or into any other
linear or switching amplifier that performs current control and provides a
bipolar, two-lead output.
Axis #1 phase A
DAC 1A
Axis #1
C=-(A+B)
DAC 1B
Axis #1 Phase B
Mtr #1
Axis #1 Phase C
MC1241
Axis #2 phase A
DAC 2A
Axis #2
C=-(A+B)
In this scheme each amplifier drives one phase of the stepper motor,
with the chipset generating the required sinusoidal waveforms in each
phase to perform smooth, accurate motion.
DAC 2B
Axis #2 Phase B
Mtr #2
Axis #2 Phase C
When using DAC output mode the digital word provided by the chipset
must first be converted into a voltage using an external DAC. Two DAC
channels are required per axis.The third phase is constructed externally
using the expression C = -(A+B). This is usually accomplished with an
Op-amp circuit.
If the chipset's PWM output mode is used the PWM magnitude and sign
signals are typically connected to an H-bridge-type device. For
maximum performance current control should be performed by the
amplifier to minimize the coil current distortion due to inductance and
back-EMF.
Although there are several methods that can be used to achieve current
control with the PWM output mode, a common method is to pass the
PWM magnitude signal through a low pass filter, thereby creating an
analog reference signal which can be directly compared with the current
through the coil.
33
Command Summary
Command Mnemonic
Axis Control
SET_1
SET_2
SET_I
Profile Generation
SET_PRFL_S_CRV
SET_PRFL_TRAP
SET_PRFL_VEL
SET_PRFL_GEAR
SET_POS
SET_VEL
SET_ACC
SET_MAX_ACC
SET_JERK
SET_RATIO
SET_START_VEL
STOP
SMOOTH_STOP
SYNCH_PRFL
GET_POS
GET_VEL
GET_ACC
GET_MAX_ACC
GET_JERK
GET_RATIO
GET_START_VEL
GET_TRGT_POS
GET_TRGT_VEL
Parameter Update
SET_TIME_BRK
SET_POS_BRK
SET_NEG_BRK
SET_ACTL_POS_BRK
SET_ACTL_NEG_BRK
SET_MTN_CMPLT_BRK
SET_EXT_BRK
SET_BRK_OFF
SET_BRK_PNT
UPDATE
MULTI_UPDATE
SET_AUTO_UPDATE_ON
SET_AUTO_UPDATE_OFF
GET_BRK_PNT
Interrupt Processing
SET_INTRPT_MASK
GET_INTRPT
RST_INTRPT
GET_INTRPT_MASK
Code
(hex)
Available
on
Axes acted on
# data words
/direction
Double
Buffered
01
02
08
all axes
all axes
all axes
set by cmd.
set by cmd.
interrupting axis
1/read
1/read
1/read
no
no
no
Set current axis # to 1
Set current axis # to 2
Set current axis # to the interrupting axis
0b
09
0a
0c
10
11
12
15
13
14
6a
46
4e
47
4a
4b
4c
4f
58
59
6b
1d
1e
all axes
all axes
all axes
all axes
all axes
all axes
all axes
all axes
all axes
all axes
all axes
all axes
all axes
all axes
all axes
all axes
all axes
all axes
all axes
all axes
all axes
all axes
all axes
current axis
current axis
current axis
current axis
current axis
current axis
current axis
current axis
current axis
current axis
current axis
current axis
current axis
current axis
current axis
current axis
current axis
current axis
current axis
current axis
current axis
current axis
current axis
0
0
0
0
2/write
2/write
2/write
1/write
2/write
2/write
2/write
0
0
0
2/read
2/read
2/read
1/read
2/read
2/read
2/read
2/read
2/read
no
no
no
no
yes
yes
yes
yes
yes
yes
no
yes
yes
yes
-
Set profile mode to S-curve
Set profile mode to trapezoidal point to point
Set profile mode to velocity-contouring
Set profile mode to electronic gear
Set command position
Set command velocity
Set command acceleration
Set max acceleration (S-curve profile only)
Set command jerk
Set command electronic gear ratio
Set starting velocity
Abruptly stop current axis motion
Smoothly stop current axis motion
Set actual position to target position
Get command position
Get command velocity
Get command acceleration
Get max. acceleration (S-curve profile only)
Get command jerk
Get command electronic gear rate
Get starting velocity
Get current target position
Get current target velocity
17
18
19
1b
1c
35
5e
6d
16
1a
5b
5c
5d
57
all axes
all axes
all axes
all axes
all axes
all axes
all axes
all axes
all axes
all axes
all axes
all axes
all axes
all axes
current axis
current axis
current axis
current axis
current axis
current axis
current axis
current axis
current axis
current axis
set by mask
current axis
current axis
current axis
0
0
0
0
0
0
0
0
2/write
0
1/write
0
0
2/read
no
no
no
no
no
no
no
no
no
no
no
-
Set breakpoint mode to time
Set breakpoint mode to pos. target position
Set breakpoint mode to neg. target position
Set breakpoint mode to pos. actual position
Set breakpoint mode to neg. actual position
Set breakpoint mode to motion complete
Set breakpoint mode to external
Set breakpoint mode off
Set breakpoint comparison value
Immediate parameter update
Multiple axis immediate parameter update
Set automatic profile update on
Set automatic profile update off
Get breakpoint comparison value
2f
30
32
56
all axes
all axes
all axes
all axes
current axis
interrupting axis
interrupting axis
current axis
1/write
1/read
1/write
1/read
no
no
-
Set interrupt mask
Get status of interrupting axis
Reset interrupting events
Get interrupt mask
34
Description
Command Mnemonic
Status/Mode
CLR_STATUS
RST_STATUS
GET_STATUS
GET_MODE
Encoder
GET_ACTL_POS
SET_CAPT_INDEX
SET_CAPT_HOME
GET_CAPT
SET_STEP_RATIO
GET_STEP_RATIO
SET_AUTO_STOP_ON
SET_AUTO_STOP_OFF
SET_POS_ERR
GET_POS_ERR
GET_ACTL_POS_ERR
Motor Control
SET_OUTPUT_PWM
SET_OUTPUT_DAC16
MTR_ON
MTR_OFF
SET_MTR_CMD
GET_MTR_CMD
SET_BUF_MTR_CMD
GET_BUF_MTR_CMD
GET_OUTPUT_MODE
Miscellaneous
SET_ACTL_POS
SET_LMT_SENSE
GET_LMT_SWTCH
LMTS_ON
LMTS_OFF
GET_HOME
RESET
GET_VRSN
GET_TIME
Microstepping
SET_PHASE_2
SET_PHASE_3
GET_PHASE_INFO
Code
(hex)
Available
on
Axes acted on
# data words
/direction
Double
Buffered
33
34
31
48
all axes
all axes
all axes
all axes
current axis
current axis
current axis
current axis
0
1/write
1/read
1/read
no
no
-
Reset status of current axis
Reset events for current axis
Get axis status word
Get axis mode word
37
64
65
36
68
6f
45
44
29
55
60
all axes
all axes
all axes
all axes
all axes
all axes
all axes
all axes
all axes
all axes
all axes
current axis
current axis
current axis
current axis
current axis
current axis
current axis
current axis
current axis
current axis
current axis
2/read
0
0
2/read
1/write
1/read
0
0
1/write
1/read
1/read
no
no
no
no
no
no
-
Get current actual axis location
Set index signal as position capture trigger
Set home signal as position capture trigger
Get current axis position capture location
Set number of encoder counts per step
Get number of encoder counts per step
Set auto stop on motion error mode on
Set auto stop on motion error mode off
Set maximum position error limit
Get maximum position error limit
Get actual position error
3c
3b
43
42
62
3a
77
69
6e
all axes
all axes
all axes
all axes
all axes
all axes
all axes
all axes
all axes
global
global
current axis
current axis
current axis
current axis
current axis
current axis
global
0
0
0
0
1/write
1/read
1/write
1/read
1/read
no
no
no
no
no
yes
-
Set motor output mode to PWM
Set motor output mode to 16-bit DAC
Enable profile generator
Disable profile generator
Write direct value to motor output
Read motor output command
Write double buffered motor cmd output
Get double buffered motor command value
Get current output mode
4d
66
67
70
71
05
39
6c
3e
all axes
all axes
all axes
all axes
all axes
all axes
all axes
all axes
all axes
current axis
global
global
global
global
global
global
global
global
2/write
1/write
1/read
0
0
1/read
0
1/read
2/read
no
no
no
no
no
-
Set axis position
Set limit switch bit sense
Get state of limit switches
Set limit switch sensing on
Set limit switch sensing off
Get state of home switches
Reset chipset
Get chipset software version information
Get current chip set time (# cycles)
74
73
7f
all axes
all axes
all axes
current axis
current axis
current axis
0
0
1/read
no
no
-
Set waveform to 2-phase
Set waveform to 3-phase
Get commutation flags set by host
35
Description
The following hex code commands are reserved for future use, or are
currently used during manufacturing/test. They return a valid checksum,
although they should not be used during normal chipset operations. The
hex command codes are: 49, 4e
Command Reference
Each command consists of a single byte, with a command code value
as described in the "encoding" description for each command. Data is
transmitted to/from the chip set in 16-bit words. All data is encoded
"high to low" i.e. each 16-bit word is encoded high byte first, low byte
second, and two word data values are encoded high word first, low
word second.
The following hex code commands are illegal, and will return a
checksum of 0. They should not be used during normal chipset
operations. The hex command codes are: 00, 03, 04, 22, 80 through ff
Unless otherwise noted, all numerical values presented in this
command summary are in decimal.
Signed data is represented in two’s complement format. In the case of
32-bit quantities, the entire 32-bit number is two's complemented. For
example to transmit the decimal number 1,234,567, which has a
hexadecimal representation of 12d687, the high word is sent first (12
hex) and then the low word is sent (d687 hex). Negative numbers are
treated in the same way. For example to transmit the decimal number
-746,455 , which has a hexadecimal value of fff49c29, then the high
word is transmitted first (fff4 hex.) followed by the low word (9c29 hex.).
Axis Control
SET_1
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
Some chipset quantities such as position are provided with ‘unity
scaling’, meaning that the value provided is used by the chipset without
internal scaling.
Other chipset quantities are scaled by various constants to allow a
more useful operating range. The non-unity scaling constants that are
used by the chipset are either 1/216 or 1/232 .
Set current axis to #1
1/read
01 (hex)
set by command
all axes
No
SET_1 changes the current axis number to 1. All commands that
operate on the current axis will be affected by this command. The
status of axis #1 is returned. See GET_STATUS command for the
status word format.
If 1/216 scaling is used then the chipset expects a number which has
been scaled by a factor of 65,536 from the ‘user’ units. For example to
specify a velocity (SET_VEL command) of 2.75 usteps/cycle time, 2.75
is multiplied by 65,536 and the result is sent to the chipset as a 32 bit
integer (180,224 dec. or 2c000 hex.). 1/216 scaling is used with 16 bit
SET_2
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
as well as 32 bit quantities. The size of the data word does not affect
how the scaling is performed.
If 1/232 scaling is indicated the chipset expects a number which has
been scaled by a factor of 4,294,967,296. For example to specify a
jerk value (SET_JERK command) of .0075 usteps/cycle time3, .0075 is
Set current axis to #2
1/read
02 (hex)
set by command
all axes
No
SET_2 changes the current axis number to 2. All commands that
operate on the current axis will be affected by this command. The
status of the axis #2 is returned. See GET_STATUS command for the
status word format.
multiplied by 4,294,967,296 and the result is sent to the chipset as a 32
bit integer (32,212,256 dec. or 1eb8520 hex).
All transmissions to/from the chip set are checksummed. The
checksum is a 16-bit quantity that can be read at the end of each
command transmission. The checksum value consists of the 16-bit sum
of all 16-bit transmissions to or from the chip set, including the
command byte which occupies the low byte of the first 16-bit
transmission word. For example if a SET_VEL command (which takes
two 16-bit words of data) was sent with a data value of fedcba98 (hex),
the checksum would be:
SET_I
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
Set current axis to interrupting axis
1/read
08 (hex)
interrupting axis
all axes
No
SET_I changes the current axis number to the interrupting axis, which
is the axis that has caused the host interrupt to become active. All
commands that operate on the current axis will be affected by this
command. The status of the interrupting axis is returned. See
GET_STATUS command for the status word format.
0011
(code for SET_VEL command)
+ fedc
(high data word)
+ ba98 (low data word)
---------1b985
check sum = b985 (keep bottom 16 bits only)
36
Profile Generation
SET_PRFL_S_CRV
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
SET_PRFL_VEL
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
Set profile mode to S-curve point to
point
none
0b (hex)
current axis
all axes
No
SET_PRFL_VEL sets the trajectory profile mode to velocity contouring.
In this mode the host specifies the command acceleration (SET_ACC
cmd), the starting velocity (SET_START_VEL cmd), and the maximum
velocity (SET_VEL cmd). Once in this mode, the trajectory profile
generator will drive the axis at the specified acceleration while not
exceeding the maximum velocity. The acceleration and the maximum
velocity may be changed on the fly. The starting velocity may not. The
axis will stay in this profile mode until another profile mode is explicitly
set. There are no limitations on changing the profile mode to velocity
contouring while the axis is in motion.
SET_PRFL_S_CRV sets the trajectory profile mode to S-curve point to
point. In this mode, the host specifies the destination position
(SET_POS cmd), the maximum velocity (SET_VEL cmd) the maximum
acceleration (SET_MAX_ACC cmd), and the jerk (SET_JERK cmd).
Once in this mode, the trajectory profile generator will drive the axis to
the destination position at the specified jerk while not exceeding the
maximum velocity and max. acceleration. The axis will stay in this
profile mode until another profile mode is explicitly set.
There are no host-specified limits on the position in this mode. It
is the responsibility of the host to specify profile parameters that
maintain the axis within safe position limits.
While in this profile mode, no parameters should be changed
while the axis is in motion.
Before setting the current profile mode to S-curve point to point,
the axis should be completely at rest.
SET_PRFL_TRAP
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
Set profile mode to velocity contouring.
none
0a (hex)
current axis
all axes
No
SET_PRFL_GEAR
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
Set profile mode to trapezoidal point to
point
none
09 (hex)
current axis
all axes
No
Set profile mode to electronic gear
none
0c (hex)
current axis
all axes
No
SET_PRFL_GEAR, sets the trajectory profile mode to electronic gear.
In this mode the host specifies the gear ratio (SET_RATIO cmd). Once
in this mode the trajectory profile generator will drive the current (slave)
axis to the position specified by the master axis factored by the
specified gear ratio. The gear ratio may be changed on the fly. The axis
will stay in this profile mode until another profile mode is explicitly set.
SET_PRFL_TRAP sets the trajectory profile mode to trapezoidal point
to point. In this mode, the host specifies the destination position
(SET_POS cmd), the maximum velocity (SET_VEL cmd), the starting
velocity (SET_START_VEL cmd), and the acceleration (SET_ACC
cmd). Once in this mode, the trajectory profile generator will drive the
axis to the destination position at the specified acceleration while not
exceeding the maximum velocity. Position and velocity may be
changed on the fly when in this profile mode; acceleration and starting
velocity may not. The axis will stay in this profile mode until another
profile mode is explicitly set.
This command will only function properly when an encoder is
attached.
There are no host-specified limits to axis motion in this mode. It is
the responsibility of the host to specify a gear ratio that maintains
the axis within safe motion limits.
SET_POS
Data/direction
Encoding:
Axis acted on:
Available on:
Double buffered:
Before setting the current profile mode to trapezoidal point to
point, the axis should be completely at rest.
While in this mode, the acceleration should not be changed until
the axis has come to a stop.
Set command position
2/write
10 (hex)
current axis
all axes
yes
SET_POS sets the final position used during the S-curve and
trapezoidal trajectory profile generator modes. The position is specified
as a signed 32-bit number with units of usteps. The range is
-1,073,741,824 to 1,073,741,823. The loaded position is not utilized
until a parameter update occurs.
37
SET_VEL
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
Set command velocity
2/write
11 (hex)
current axis
all axes
yes
SET_JERK
Data written:
Data read:
Encoding:
Axis acted on:
Available on:
Double buffered:
SET_VEL sets the maximum velocity magnitude used during the Scurve, trapezoidal, and velocity contouring profile modes. The velocity
is specified as an unsigned 32-bit number with units of usteps/cycle.
The data word scaling is 1/216. The range is 0 to +1,073,741,823. The
SET_JERK sets the command jerk used during the S-curve profile
generation mode. The jerk is specified as an unsigned 32-bit number
with units of usteps/cycle3. The scaling is 1/232. The range is 0 to
loaded velocity is not utilized until a parameter update occurs.
SET_ACC
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
2,147,483,647. The loaded jerk is not utilized until a parameter update
occurs.
Set command acceleration
2/write
12 (hex)
current axis
all axes
yes
SET_RATIO
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
SET_ACC sets the command acceleration. When in trapezoidal pointto-point mode, the acceleration is specified as an unsigned 32-bit
number with units of usteps/cycle2, represented using 1/216 scaling.
Set command gear ratio
2/write
14 (hex)
current axis
all axes
yes
SET_RATIO sets the electronic gear ratio used by the trajectory profile
generator. It is used when the profile mode is set to electronic gear. The
gear ratio is specified as a signed 32-bit number with 1/216 scaling. The
The range is 0 to +1,073,741,823. When in the velocity contouring
mode, the acceleration is specified as a signed 32-bit number with units
of usteps/cycle2, represented in 1/216 format.The range is -
range is -1,073,741,824 to +1,073,741,823. The specified ratio value is
defined as the number of microsteps per encoder count with a positive
number indicating motion in the same direction. For example a value of
+8000 hex (1/2) will result in 1 microstep in the positive direction for
each two encoder counts in the positive direction, and a value of FFFE0000 hex (-2) will result in 2 microsteps in the negative direction
for each encoder count in the positive direction. The loaded ratio is not
utilized until a parameter update occurs.
1,073,741,824 to +1,073,741,823. The loaded acceleration is not
utilized until a parameter update occurs.
This command is used when the profile mode is set to trapezoidal
point-to-point or velocity contouring.
SET_MAX_ACC
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
Set command jerk
2 words
none
13 (hex)
current axis
all axes
yes
This command will only function properly when an encoder is
attached.
Set maximum acceleration
1/write
15 (hex)
current axis
all axes
yes
SET_START_VEL
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
SET_MAX_ACC sets the maximum acceleration. The acceleration is
specified as an unsigned 16-bit number with units of usteps/cycle2
represented using 1/216 scaling. The range is 0 to +1,073,741,823. The
loaded max. acceleration is not utilized until a parameter update occurs.
Set starting velocity
2/write
6a (hex)
current axis
all axes
no
SET_START_VEL sets the minimum allowed velocity. This command
is used during the trapezoidal and velocity contouring profile modes,
and is useful in conjunction with systems that may be induced to
oscillate if operated at too low a speed. The starting velocity is specified
as an unsigned 32-bit number with units of usteps/cycle. The data word
scaling is 1/216. The range is 0 to +1,073,741,823.
This command is used when the profile mode is set to S-curve
point to point.
The starting velocity must always be smaller than the maximum
velocity set using the SET_VEL command.
This command is not used with the S-curve and electronic gear
profile modes.
38
The starting velocity parameter is not double buffered. It takes
affect immediately, not after an UPDATE command.
STOP
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
GET_POS
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
Abruptly stop current axis motion
none
46 (hex)
current axis
all axes
yes
GET_POS returns the destination position set using the SET_POS
command. It returns the double-buffered value (set directly by the host),
which may or may not correspond to the active value, depending on
whether the profile parameters have been updated. The returned
position is a signed 32-bit number with units of usteps.
STOP, also known as CLR_PRFL in earlier chipset versions, stops the
current axis by setting the target velocity to zero. This function will not
be performed until a parameter update occurs. After the update occurs
the axis trajectory generator will stop and the motion complete bit will
be set. This command is useful for stopping the axis abruptly.
SMOOTH_STOP
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
GET_VEL
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
Smoothly stop current axis motion
none
4e (hex)
current axis
all axes
yes
usteps/cycle.
GET_ACC
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
This command does not function when the profile mode is set to
Electronic Gear.
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
Get command velocity
2/read
4b (hex)
current axis
all axes
-
GET_VEL returns the maximum velocity set using the SET_VEL
command. It returns the double-buffered value (set directly by the host),
which may or may not correspond to the active value, depending on
whether the profile parameters have been updated. The returned
velocity is an unsigned 32-bit number in 1/216 format with units of
SMOOTH_STOP stops the current axis by setting the desired velocity
to zero, resulting in a controlled deceleration of the axis eventually to a
velocity of 0. The deceleration profile will mirror the acceleration profile
for the current profile mode. For example if the SMOOTH_STOP
command is given during an s-curve profile the deceleration profile may
have up to three phases, depending on the # of phases during the
acceleration profile, and if the SMOOTH_STOP command is given
during a trapezoidal profile or a velocity mode profile the deceleration
will be linear, with a value equal to the acceleration parameter.
SYNCH_PRFL
Get command position
2/read
4a (hex)
current axis
all axes
-
Get command acceleration
2/read
4c (hex)
current axis
all axes
-
GET_ACC returns the acceleration value set using the SET_ACC
command. It returns the double-buffered value (set directly by the host),
which may or may not correspond to the active value, depending on
whether the profile parameters have been updated. The returned
position is either an unsigned 32-bit number in 1/216 format with units
Set target position equal to the actual
position
none
47 (hex)
current axis
all axes
yes
of usteps/cycle2, or a signed 32 bit number in 1/216 format with units of
usteps/cycle2.
This command is used when the profile mode is set to trapezoidal
point-to-point or velocity contouring.
SYNCH_PRFL sets the trajectory profile generator target position (in
microsteps) equal to the actual axis position (in encoder counts),
clearing the following error. This command is available for all profile
types. This function will not be performed until a parameter update
occurs.
The SYNCH_PRFL command does not set the target velocity to
zero. If it is desired that the axis not move after a SYNCH_PRFL
command then a STOP command, in addition to the SYNCH_PRFL
command should be used.
39
GET_MAX_ACC
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
Get maximum acceleration
1/read
4f (hex)
current axis
all axes
-
GET_TRGT_POS
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
GET_MAX_ACC returns the max. acceleration value set using the
SET_MAX_ACC command. It returns the double-buffered value (set
directly by the host), which may or may not correspond to the active
value, depending on whether the profile parameters have been
updated. The returned acceleration is an unsigned 16-bit number in
1/216 format with units of usteps/cycle2.
Return target position
2/read
1d (hex)
current axis
all axes
-
GET_TRGT_POS returns the current desired position value being
generated by the trajectory profile generator. This value represents the
target position for the axis at the current cycle time, i.e. the position
being output by the trajectory profile generator at the time of the
command. This command operates for all profile modes. The value
returned is a 32-bit signed number with units of usteps. The range is 1,073,741,824 to 1,073,741,823.
This command is used when the profile mode is set to S-curve
point to point.
GET_JERK
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
GET_TRGT_VEL
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
Get command jerk
2/read
58 (hex)
current axis
all axes
-
GET_TRGT_VEL returns the current desired velocity value being
generated by the trajectory profile generator. This value represents the
target velocity for the axis at the current cycle time, i.e. the velocity
being output by the trajectory profile generator at the time of the
command. This command operates for all profile modes. The value
returned is a 32 bit signed number with units of usteps/cycle,
represented in 1/216 format. The range is -1,073,741,824 to
GET_JERK returns the jerk value set using the SET_JERK command.
It returns the double-buffered value (set directly by the host), which may
or may not correspond to the active value, depending on whether the
profile parameters have been updated. The returned jerk is an
unsigned 32-bit number with 1/232 scaling with units of usteps/cycle3.
GET_RATIO
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
+1,073,741,823.
Get command gear ratio
2/read
59 (hex)
current axis
all axes
-
Parameter Update
SET_TIME_BRK
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
GET_RATIO returns the gear ratio set using the SET_RATIO
command. It returns the double-buffered value (set directly by the host),
which may or may not correspond to the active value, depending on
whether the profile parameters have been updated. The returned ratio
is a signed 32-bit number in 1/216 format.
GET_START_VEL
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
Return target velocity
2/read
1e (hex)
current axis
all axes
-
Set break point mode to time based
none
17 (hex)
current axis
all axes
no
SET_TIME_BRK sets the current breakpoint mode to time based. In
this mode the value loaded into the breakpoint register (SET_BRK_PNT
cmd) will represent the number of cycles since chip set power on. After
the SET_TIME_BRK command is executed, at each loop the break
point value will be compared against the current chip set time. If the
values are equal all double-buffered parameters will be loaded in to the
active registers. See GET_TIME cmd for information on the chip set
time. After this breakpoint condition has been satisfied, the breakpoint
mode is reset i.e. no additional breakpoints will occur until a new
breakpoint condition is set.
Get starting velocity
2/read
6b (hex)
current axis
all axes
-
GET_START_VEL returns the starting velocity set using the
SET_START_VEL command. The returned starting velocity is an
unsigned 32-bit number using 1/216 scaling with units of usteps/cycle.
40
SET_POS_BRK
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
SET_ACTL_NEG_BRK
Set break point mode to positive target
position based
none
18 (hex)
current axis
all axes
no
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
Set break point mode to negative actual
position based
none
1c (hex)
current axis
all axes
no
SET_POS_BRK sets the current breakpoint mode to positive target
position based. In this mode the value loaded into the breakpoint
register (SET_BRK_PNT cmd) will represent the axis position in usteps.
After the SET_POS_BRK command is executed, at each cycle the
break point value will be compared against the current axis target
position. If the target position has a value equal to or greater than the
breakpoint register then all double-buffered parameters will be loaded in
to the active registers. After this breakpoint condition has been
satisfied, the breakpoint mode is reset i.e. no additional breakpoints will
occur until a new breakpoint condition is set.
SET_ACTL_NEG_BRK sets the current breakpoint mode to negative
actual position based. In this mode the value loaded into the breakpoint
register (SET_BRK_PNT cmd) will represent the axis position in usteps
After the SET_ACTL_NEG_BRK command is executed, at each cycle
the break point value will be compared against the current axis actual
position. If the actual position has a value equal to or less than the
breakpoint register then all double-buffered parameters will be loaded
into the active registers. After this breakpoint condition has been
satisfied, the breakpoint mode is reset i.e. no additional breakpoints will
occur until a new breakpoint condition is set.
SET_NEG_BRK
SET_MTN_CMPLT_BRK Set break point mode to motion
complete
Data/direction:
none
Encoding:
35 (hex)
Axis acted on:
current axis
Available on:
all axes
Double buffered:
no
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
Set break point mode to negative target
position based
none
19 (hex)
current axis
all axes
no
SET_NEG_BRK sets the current breakpoint mode to negative target
position based. In this mode the value loaded into the breakpoint
register (SET_BRK_PNT cmd) will represent the axis position in usteps
After the SET_NEG_BRK command is executed, at each cycle the
break point value will be compared against the current axis target
position. If the target position has a value equal to or less than the
breakpoint register then all double-buffered parameters will be loaded
into the active registers. After this breakpoint condition has been
satisfied, the breakpoint mode is reset i.e. no additional breakpoints will
occur until a new breakpoint condition is set.
SET_MTN_CMPLT_BRK sets the current breakpoint mode to motion
complete. In this mode the breakpoint condition is satisfied when the
motion complete bit in the axis status word becomes active (axis motion
is complete). This breakpoint mode is useful for immediately starting a
new profile at the end of the current profile. Once the motion complete
bit becomes active all double-buffered parameters will be loaded in to
the active registers. After this breakpoint condition has been satisfied,
the breakpoint mode is reset i.e. no additional breakpoints will occur
until a new breakpoint condition is set.
No 32-bit compare value is required to be loaded when using this
breakpoint mode.
SET_ACTL_POS_BRK
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
Set break point mode to positive actual
position based
none
1b (hex)
current axis
all axes
no
It is the responsibility of the host to ensure that the motion
complete bit is not set when this breakpoint is initiated.
SET_EXT_BRK
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
SET_ACTL_POS_BRK sets the current breakpoint mode to positive
actual position based. In this mode the value loaded into the breakpoint
register (SET_BRK_PNT cmd) will represent the axis position in usteps.
After the SET_ACTL_POS_BRK command is executed, at each cycle
the break point value will be compared against the current axis actual
position. If the actual position has a value equal to or greater than the
breakpoint register then all double-buffered parameters will be loaded in
to the active registers. After this breakpoint condition has been
satisfied, the breakpoint mode is reset i.e. no additional breakpoints will
occur until a new breakpoint condition is set..
Set break point mode to external
none
5e (hex)
current axis
all axes
no
SET_EXT_BRK sets the current breakpoint mode to external. In this
mode the breakpoint condition is satisfied when the home signal for the
current axis becomes active (goes low). This breakpoint mode is useful
for executing a profile change based on some external signal condition.
Once the home signal becomes active all double-buffered parameters
will be loaded in to the active registers. After this breakpoint condition
41
has been satisfied, the breakpoint mode is reset i.e. no additional
breakpoints will occur until a new breakpoint condition is set.
MULTI_UPDATE
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
No 32-bit compare value is required to be loaded when using this
breakpoint mode.
SET_BRK_OFF
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
Set break point mode off
none
6d (hex)
current axis
all axes
no
MULTI_UPDATE immediately updates the double-buffered parameters
for 1 or more axis simultaneously. For each updated axis, the axis
behaves as if a separate UPDATE command had been given for each
axis. The associated data word contains a "positive-sense" bit mask for
each axis. A one (1) in the axis bit position indicates the axis will be
updated. A zero (0) indicates it will not. The following table shows this
bit encoding:
SET_BRK_OFF sets the breakpoint mode to "off". Any breakpoint
mode that has been set previously (SET_TIME_BRK, SET_POS_BRK,
SET_NEG_BRK, SET_ACTL_POS_BRK or SET_ACTL_NEG_BRK)
and is still active (the breakpoint condition has not occurred), is
disabled with this command. After this command has been executed no
additional breakpoints will occur until a new breakpoint condition is set.
SET_BRK_PNT
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
Bit #
0
1
2-15
Set break point comparison value
2/write
16 (hex)
current axis
all axes
no
Axis # updated
1
2
unused, must be set to 0
SET_AUTO_UPDATE_ON
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
SET_BRK_PNT sets the breakpoint comparison value. Its contents are
interpreted based on the type of breakpoint set; time based
(SET_TIME_BRK cmd) or position based (SET_POS_BRK cmd,
SET_NEG_BRK cmd, SET_POS_ACTL_BRK cmd, and
SET_NEG_ACTL_BRK cmd). When set to time-based the loaded value
is compared with the current chip set time at each cycle, and the value
loaded is a 32-bit number with units of cycles. When set to positionbased the loaded value is compared with the current axis target or
actual position at each cycle, and the value loaded is a 32-bit number
with units of usteps.
UPDATE
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
Immediately update parameters for
multiple axis
1/write
5b (hex)
set by data word
all axes
no
Set automatic profile update on
none
5c (hex)
current
all axes
no
SET_AUTO_UPDATE_ON sets the automatic profile update
mechanism on. After this command is sent, a satisfied breakpoint
condition will result in all of the double-buffered parameters
automatically being transferred to the active registers. Once set to this
mode, the axis will stay in this mode until explicitly commanded out
using the SET_AUTO_UPDATE_OFF command.
SET_AUTO_UPDATE_OFF
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
Immediately update parameters
none
1a (hex)
current axis
all axes
no
Set automatic profile update off
none
5d (hex)
current
all axes
no
SET_AUTO_UPDATE_OFF sets the automatic profile update
mechanism off. After this command is sent, a satisfied breakpoint
condition will not result in the double-buffered parameters automatically
being transferred to the active registers. Once set to this mode, the axis
will stay in this mode until explicitly commanded out using the
SET_AUTO_UPDATE_ON command.
UPDATE immediately updates all double buffered parameters.
When in this mode, the only way that profile parameters can be
updated is through the UPDATE or the MULTI_UPDATE
commands.
42
GET_BRK_PNT
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
Get break point comparison value
2/read
57 (hex)
current axis
all axes
no
GET_INTRPT
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
GET_BRK_PNT returns the breakpoint comparison value set using the
SET_BRK_PNT command. The returned value is a 32-bit number with
units of either cycles or usteps (depending on the current breakpoint
mode).
GET_INTRPT returns the status of the axis that generated a host
interrupt. The current axis number will not be changed after executing
this command. See GET_STATUS for a definition of the returned status
word. If this command is executed when no interrupt condition is
present, the status of the current axis will be returned.
Interrupt Processing
SET_INTRPT_MASK
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
If this command is executed when no interrupt condition is
present, the command will return the status of the current axis
(same as GET_STATUS command).
Set host interrupt mask
1/write
2f (hex)
current axis
all axes
no
RST_INTRPT
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
SET_INTRPT_MASK sets the interrupt mask so that interrupt events
can be individually masked off. When a non-masked interrupt occurs in
any axis, the interrupt signal to the host is activated (HostIntrpt pin on
I/O chip). The host can choose to ignore or respond to the interrupt.
Once an interrupt has been generated, no new interrupts will be
generated until a RST_INTRPT command is given, after which the
interrupt signal to the host will be cleared, and a new interrupt (on any
axis) can be generated. The associated data word is encoded as a field
of bits, with each bit representing a possible interrupting condition. A 1
value in the mask bit will cause the corresponding event to generate an
interrupt, while a 0 will stop the corresponding event from interrupting
the host. The bit encoding is as follows:
Bit #
0
1
2
3
4
5
6
7
8-15
Return status of the interrupting axis
1/read
30 (hex)
interrupting axis
all axes
-
Reset interrupting condition events
1/write
32 (hex)
interrupting axis
all axes
no
RST_INTRPT resets (clears) the interrupt condition bits for the axis that
caused a host interrupt by masking the interrupting axis status word
with the specified data word. In addition, the host interrupt signal
(HostIntrpt pin on I/O chip) is de-activated.The data word is encoded as
a field of bits, with each bit representing a possible interrupting
condition. For each status word event bit a 1 value in the specified word
will cause the status bit to remain unchanged, while a 0 will reset the
corresponding event. The bit encoding is as follows:
Bit #
0
1
2
3
4
5
6
7
8-15
Event
Motion complete
position wrap-around
update breakpoint reached
position capture received
motion error
positive limit switch
negative limit switch
command error
not used, must be set to 0
Event
Motion complete
position wrap-around
breakpoint reached
position capture received
motion error
positive limit switch
negative limit switch
command error
not used, may be set to 0 or 1
If this command is executed when no interrupt condition is
present, the command will have no effect.
43
GET_INTRPT_MASK
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
Get host interrupt mask
1/read
56 (hex)
current axis
all axes
no
GET_STATUS
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
GET_INTRPT_MASK returns the interrupt mask set by the
SET_INTRPT_MASK command. The returned value is a bit-encoded
mask, described in the SET_INTRPT_MASK command.
GET_STATUS returns the status of the current axis.The bit encoding of
the returned word is as follows:
Bit #
0
1
2
3
Status/Mode
CLR_STATUS
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
Clear all event bit conditions
none
33 (hex)
current axis
all axes
no
4
5
6
7
8
9
10
11
12,13
14,15
CLR_STATUS resets (clears) all of the event bit conditions for the axis
(bits 0-7 of the status word). The host interrupt line is not affected by
this command. This command is useful for clearing all event bits during
initialization, or during on-line usage if the interrupt line and associated
commands are not being used. For a detailed description of the status
word event bits, see the GET_STATUS command.
This command does not affect the status of the host interrupt line,
only the status event-bits themselves. To reset the host interrupt
line, a RST_INTRPT command must be sent.
RST_STATUS
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
Event
motion complete (1 indicates complete)
position wrap-around (1 indicates wrap)
update breakpoint reached (1 indicates reached)
position capture received (1 indicates capture has
occurred)
motion error (1 indicates motion error)
positive limit switch (1 indicates limit switch trip)
negative limit switch (1 indicates limit switch trip)
command error (1 indicates command error)
motor on/off status (1 indicates on)
axis on/off status (1 indicates on)
In-motion bit (1 indicates axis is in motion)
reserved (may be 0 or 1)
current axis # (13 bit = high bit, 12 bit = low bit)
reserved (may be 0 or 1)
Bits 0-7 are set by the chipset, and must be reset by the host
(using CLR_STATUS, RST_STATUS, or RST_INTRPT commands).
Bits 8, 9, 10, 12, and 13 are continuously maintained by the chipset
and are not set or reset by the host.
Reset specific event bit conditions
1/write
34 (hex)
current axis
all axes
no
GET_MODE
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
RST_STATUS resets (clears) the condition event bits for the current
axis, using a data word mask. The data word is encoded as a field of
bits, with each bit representing a possible condition event. For each
status word event bit a 1 value in the specified data word will cause the
status bit to remain unchanged, while a 0 will reset the corresponding
event. The bit encoding is as follows:
Bit #
0
1
2
3
4
5
6
7
8-15
Get axis status word
1/read
31 (hex)
current axis
all axes
-
Get axis mode word
1/read
48 (hex)
current axis
all axes
-
GET_MODE returns the mode word for the axis.The bit encoding of the
returned word is as follows:
Bit #
0-6
7
Event
Motion complete
position wrap-around
breakpoint reached
position capture received
motion error
positive limit switch
negative limit switch
command error
not used, may be set to 0 or 1
8
9
10
44
Event
Contains no host-useable information.
Stop on motion error mode flag. 1 indicates auto
stop is on.
Internal use only. Contains no host-useable data
Contains no host-useable information
Auto update flag. 1 indicates auto update is
disabled.
11,12
13-15
Trajectory profile mode, encoded as follows:
Bit 12
Bit 11
Profile Mode
0
0
trapezoidal
0
1
velocity contouring
1
0
s-curve
1
1
electronic gear
Phase # (S-curve profile only). 3-bit word encodes
phase #. Bit 15 is MSB, bit 13 is LSB.
GET_CAPT
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
GET_CAPT returns the current value of the high-speed position capture
register, as well as resets the capture hardware so that subsequent
positions may be captured. The value returned is a 32 bit signed
number with units of encoder counts.
Encoder
GET_ACTL_POS
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
This command will only function properly when an encoder is
attached.
Return actual axis position
2/read
37 (hex)
current axis
all axes
-
SET_STEP_RATIO
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
GET_ACTL_POS returns the current encoder position of the current
axis. The value read is up to date to within a cycle time.The value
returned is a 32 bit signed number with units of encoder counts.
SET_CAPT_INDEX
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
Set position capture trigger source to
the index signal
none
64 (hex)
current axis
all axes
no
encoder counts per motor rotation, and Nmicrosteps is the number of
output microsteps per motor rotation (12,800 for a 1.8 degree stepper,
3,200 for a 7.2 degree stepper). Using this equation the resultant ratio
must be an exact integer.
GET_STEP_RATIO
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
This command will only function properly when an encoder is
attached.
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
Set number of encoder counts per ustep
none
68 (hex)
current axis
all axes
no
SET_STEP_RATIO sets the ratio of encoder counts to output
microsteps for the current axis used in conjunction with automatic stall
detection. The specified ratio is a 16-bit unsigned number with a range
of 0 to 32,767. The formula that should be used to set this value is:
Ratio = (Ncounts/Nmicrosteps)*256. Where Ncounts is the number of
SET_CAPT_INDEX sets the high-speed position register trigger source
for the current axis to the index signal. When the index is used as the
trigger source, it is gated by the A and B quadrature signals (see Pin
Descriptions Section of this manual for details).
SET_CAPT_HOME
Return high speed capture register
2/read
36 (hex)
current axis
all axes
-
Get number of encoder counts per ustep
none
6f (hex)
current axis
all axes
-
GET_STEP_RATIO returns the ratio of encoder counts to output
microsteps set using the SET_STEP_RATIO command. The returned
value is a 16-bit unsigned number.
Set position capture trigger source to
the home signal
none
65 (hex)
current axis
all axes
no
SET_AUTO_STOP_ON
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
SET_CAPT_HOME sets the high-speed position register trigger source
to the home signal.
This command will only function properly when an encoder is
attached.
Enable automatic motor shutdown
none
45 (hex)
current axis
all axes
no
SET_AUTO_STOP_ON enables automatic profile generation shutdown
upon motion error. In this mode profile generation will be disabled
(equivalent to MTR_OFF cmd) when a motion error occurs (see
45
SET_POS_ERR cmd for more info.). The profile generator can be reenabled using the MTR_ON cmd.
SET_AUTO_STOP_OFF
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
step ratio parameters (set using SET_STEP_RATIO command). The
returned value is a signed 16-bit number with units of encoder counts.
The range is -32,768 to +32,767.
Disables automatic motor shutdown
none
44 (hex)
current axis
all axes
no
Motor
SET_OUTPUT_PWM
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
SET_AUTO_STOP_OFF disables automatic profile generator
shutdown upon motion error. In this mode the profile generator will not
be disabled when a motion error occurs.
SET_POS_ERR
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
SET_OUTPUT_PWM sets the motor output mode to PWM. PWM mode
outputs the motor output value on 2 output signals (sign and
magnitude) for each enabled axis. This command affects the output
mode for all axes.
Set position error limit
1/write
29 (hex)
current axis
all axes
no
SET_OUTPUT_DAC16
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
SET_POS_ERR sets the position error limit for the automatic stall
detection facility. The error is specified as an unsigned 16-bit number
with units of encoder counts The range is 0 to 32,767. At each chipset
cycle the magnitude of the position error calculated by the stall detector
is compared with the specified position error limit. If the actual position
error exceeds the specified value, the motion error status bit is set. In
addition, if the axis has been set for automatic motor stop upon motion
error, the axis profile generation will be disabled. The loaded maximum
position error is utilized immediately. No update is required for this
command to take effect.
GET_POS_ERR
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
Set motor output mode to 16-bit DAC
none
3b (hex)
global (all axes)
all axes
no
SET_OUTPUT_DAC16 sets the motor output mode to 16-bit DAC. This
motor output mode uses a 16-bit data bus, along with various control
signals to load a DAC value for each enabled axis. This command
affects the output mode for all axes.
MTR_ON
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
Get maximum position error
1/read
55 (hex)
current axis
all axes
-
Enable profile generation
none
43 (hex)
current axis
all axes
no
MTR_ON enables the profile generator . When the profile generator is
enabled, phased sine-wave signals are generated by the trajectory
generator and output on the motor output signal lines. When it is
disabled the sine-wave position is 'frozen' and no motion can occur until
it is enabled.
GET_POS_ERR returns the maximum position error value set using the
SET_POS_ERR command. The returned maximum position error value
is an un signed 16-bit number with units of encoder counts.
GET_ACTL_POS_ERR
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
Set motor output mode to PWM
none
3c (hex)
global (all axes)
all axes
no
After a MTR_ON command the pulse generator will be inactive
until a trajectory move is made by the host.
Return current position error
1/read
60 (hex)
current axis
all axes
-
GET_ACTL_POS_ERR returns the current instantaneous position error
of the axis. The returned value represents the difference between the
actual position and the target position after the target motion, which has
units of microsteps has been converted into encoder counts using the
46
MTR_OFF
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
Disable profile generation
none
42 (hex)
current axis
all axes
no
SET_BUF_MTR_CMD
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
MTR_OFF disables profile generation. When profile generation is
disabled the sine-wave position is 'frozen' and no motion can occur until
it is enabled. When the profile generator is enabled, phased sine-wave
signals are generated by the trajectory generator and output on the
motor output signal lines.
SET_BUF_MTR_CMD loads the motor command register with the
specified value. It is identical to the SET_MTR_CMD except that it
requires an UPDATE command for the specified value to take effect.
Unless the motor command value is explicitly changed using the
SET_MTR_CMD or SET_BUF_MTR_CMD commands, after a
MTR_OFF command the motor will hold position
SET_MTR_CMD
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
GET_BUF_MTR_CMD
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
Write motor command value
1/write
62 (hex)
current axis
all axes
no
Get double-buffered motor output value
1/read
69 (hex)
current axis
all axes
-
GET_BUF_MTR_CMD returns the value set using the
SET_BUF_MTR_CMD. The returned value is a 16 bit integer.
GET_OUTPUT_MODE
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
SET_MTR_CMD loads the motor command register with the specified
value. This register controls the amplitude of the microstepping signals
that are sent to the motor. The specified motor command is a 16-bit
signed number with range -32,767 to +32,767. Regardless of the motor
output mode (PWM or DAC16), a value of -32,767 represents the
largest negative direction motor level , a value of 0 represents no motor
(0) output level, and a value of 32,767 represents the largest positive
motor level.
GET_MTR_CMD
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
Write double-buffered value to motor
output
1/write
77 (hex)
current axis
all axes
yes
Get current motor output mode
1/read
6e (hex)
global (all axes)
all axes
-
GET_OUTPUT_MODE returns the current motor output mode set using
the SET_OUTPUT_PWM and SET_OUTPUT_DAC16 commands. The
returned 16 bit word contains the motor output mode. The encoding is
as follows:
Get motor command value
1/read
69 (hex)
current axis
all axes
-
Returned Word Value
0
1
2
GET_MTR_CMD returns the value of the motor command register. This
value will be equal to the value set after a SET_MTR_CMD command,
or after a SET_BUF_MTR_CMD with a subsequent UPDATE
command. The returned value is a 16 bit integer.
Output Mode
PWM
not used
DAC16
Miscellaneous
SET_ACTL_POS
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
Set actual axis position
2/write
4d (hex)
current axis
all axes
no
SET_ACTL_POS sets the current actual position (in encoder counts) as
well as the current target position (in microsteps) to the specified value.
The desired position is specified as a signed 32 bit number with an
allowed range of -1,073,741,824 to 1,073,741,823.
47
This command causes the actual position error to be set to 0.
LMTS_ON
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
The loaded position is utilized immediately. No UPDATE is
required for the command to take effect.
SET_LMT_SENSE
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
Set limit switch bit sense
1/write
66 (hex)
global (all axes)
all axes
-
LMTS_ON turns the limit switch sensing mechanism on. LMTS_ON reenables limit switch sensing whenever it has been disabled using the
LMTS_OFF command.
LMTS_OFF
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
SET_LMT_SENSE sets the interpretation of the limit switch input bits.
This command provides added flexibility in interfacing to various
switch/sensor components. The signal level interpretation for the
positive and negative switch inputs are bit-programmable. A 0 in the
corresponding bit of the sense word indicates that the input will be
active high. A 1 in the sense word indicates that the input will be active
low. The sense word is encoded as follows:
Bit #
0
1
2
3
4-15
This command only disables the automatic setting of the negative
and positive limit switch bits in the status word. It does not affect
the status of these bits if they have already been set, nor does it
affect the GET_LMT_SWTCH command.
GET_HOME
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
The above bits are encoded as shown for the MC1241A. For the
MC1141A axis 2 is not used.
Get state of over-travel limit switches
1/read
67 (hex)
global (all axes)
all axes
-
Get state of home signal inputs
1/read
05 (hex)
global (all axes)
all axes
-
GET_HOME returns the value of the home signal inputs for all valid
axes. The returned word is encoded as follows:
Bit #
0
1
2-15
GET_LMT_SWTCH returns the value of the limit switch input signals
for all valid axis. The returned word is encoded as follows:
Bit #
0
1
2
3
4-15
Set limit switch sensing off
none
71 (hex)
global (all axes)
all axes
-
LMTS_OFF turns the limit switch sensing mechanism off. LMTS_OFF
is used whenever it is desired that limit switch sensing not be active.
Description
Axis 1 positive limit switch (0 = active high)
Axis 1 negative limit switch (0 = active high)
Axis 2 positive limit switch (0 = active high)
Axis 2 negative limit switch (0 = active high)
not used (must set to 0)
GET_LMT_SWTCH
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
Set limit switch sensing on
none
70 (hex)
global (all axes)
all axes
-
Description
Axis 1 positive limit switch (1 = high)
Axis 1 negative limit switch (1 = high)
Axis 2 positive limit switch (1 = high)
Axis 2 negative limit switch (1 = high)
not used (set to 0)
Description
Axis 1 home signal (1 = high)
Axis 2 home signal (1 = high)
not used (set to 0)
The above bits are encoded as shown for the MC1241A. For the
MC1141A Axis 2 will always be set to 0.
RESET
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
The above bits are encoded as shown for the MC1241A. For the
MC1141A Axis 2 will always be set to 0.
The values returned by this command are not affected by the
SET_LMT_SENSE command.
Reset chip set
none
39 (hex)
global (all axes)
all axes
No
RESET resets the entire chip set. This command performs the same
sequence as a hardware reset. At the end of this operation the chip set
will be in the default or powerup condition, defined as follows:
48
8-10
Condition
all actual axis positions
all capture registers
all event conditions
host interrupt (HostIntrpt) signal
all interrupt masks
all profile modes
all filter modes
all profile parameter values
all filter gains
all integration limits
all max. position error values
all brkpnt comparison values
auto update
all axes status'
all motor status'
all auto stop modes
limit switch sensing
limit switch sense register
output mode
all motor output values
current axis number
cycle time
all waveforms
all initial phase offsets
all # counts per comm. cycle
all phase init methods
all commutation modes
all prescalars
all phase advance gains
Hall sense register
all phase init durations
Initial Value
0
0
cleared
not active
0
trapezoidal
PID
0
0
32767
32767
0
enabled (on)
enabled (on)
enabled (on)
enabled (on)
enabled (on)
0 (all active high)
PWM
0
1
4 - MC1241A
2 - MC1141A
3-phase
ffff (hex)
0
algorithmic
encoder-based
disabled
0
0 (all active high)
0
11-13
14-15
For example, the returned version code for the MC1401 (version 1.0
software) is 5908 (hex), the returned version code for the MC1201-P
(version 1.0 software) is 4928, and the returned version code for the
MC1241 (version 1.3 software) is 4a0b
GET_TIME
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
Microstepping
SET_PHASE_2
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
5-7
Set waveform mode to 2-phase
none
74 (hex)
global
all
no
SET_PHASE_2 sets the current microstepping waveform to 2-phase.
With this waveform the microstepping output signals have a phase
separation of 90 degrees, and can be used with standard 2-phase
stepper motors.
2-Phase mode is the standard waveform mode for most stepper
motors.
Return chipset software information
1read
6c (hex)
global (all axes)
all axes
-
SET_PHASE_3
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
GET_VRSN returns various information on the chipset part number and
software version. The encoding is as follows:
Bit #
0-2
3-4
Return current chip set time.
2/read
3e (hex)
global (all axes)
all axes
-
GET_TIME returns the current system time, expressed as the number
of cycles since chip set power on.The chip set clock starts at 0 after a
power on or reset and will count indefinitely, wrapping from a value of
4,294,967,295 to 0. The returned value is a 32 bit number with units of
cycle times.
After a reset (software or hardware) the chipset requires at least 2
milliseconds before it can accept another host I/O command
GET_VRSN
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
part number code 0 = 00 (MC1400-series), 1 = 01
(MC1401-series), 2 = 31 (MC1241-series) , 3 = 41
(MC1241-series), 4 = 51 (MC1451-series)
# axes supported (0 = 1)
generation # (1)
Interpretation
minor software version
major software version. Major software versions 2
and above indicate 'A' versions parts
"dash" version # (no dash = 0, -P = 1
Set waveform to 3-phase
none
73 (hex)
global
all
no
SET_PHASE_3 sets the current microstepping waveform to 3-phase.
With this waveform the microstepping output signals have a phase
separation of 120 degrees, and can be used with 3-phase stepper
motors or 3-phase AC Induction motors.
49
GET_PHASE_INFO
Data/direction:
Encoding:
Axis acted on:
Available on:
Double buffered:
Get microstepping flags set by host.
1/read
7f (hex)
current axis
all
-
GET_PHASE_INFO returns the state of various microstepping-related
flags maintained by the chipset. The returned word is a 16-bit word
encoded as follows:
Bit #
0- 2
3
4-15
Interpretation
used internally by chipset
Waveform (0 = 3-phase, 1 = 2-phase)
used internally by chipset
50
NOTES
51
Application Notes
Interfacing MC1241A to ISA bus.
A complete, ready-to-use ISA (PC/AT) bus interface circuit has been
provided to illustrate MC1241A host interfacing, as well as to make it
easier for the customer to build an MC1241-based system.
The interface between the PMD MC1241A chip set and the ISA (PCAT) Bus is shown on the following page.
Comments on Schematic
This interface uses a 22V10 PAL and a 74LS245 to buffer the data
lines.This interface assumes a base address is assigned in the address
space of A9-A0. 300-400 hex These addresses are generally available
for prototyping and other system-specific uses without interfering with
system assignments. This interface occupies 16 addresses from XX0 to
XXF hex though it does not use all the addresses. Two select lines are
provided allowing the base address to be set to 340,350,370 and 390
hex for the select lines S1,S0 equal to 0,1,2,and 3 respectively.The
address assignments used are as follows, where BADR is the base
address, 340 hex for example:
Address
340h
342h
344h
348h
use
read-write data
write command
read status (HostRdy) [D7 only]
write reset [Data= don't care]
The base address (BADR) is decoded in ADRDEC. It is nanded with
SA2:SA3, BADR+0, (B+0) to form -HSEL to select the I/O chip. B+0
nanded with IOR* forms -HRD, host read, directly. The 22V10 tail-bites
the write pulse since the setup time is greater than necessary on the
bus some of the bus duration is used to generate data hold time at the
I/O chip. -HWR, host write is set the first clock after B+0 and IOW* is
recognized. The next clock sets TOG and clears -HWR. TOG remains
set holding -HWR clear until IOW* is unasserted on the bus indicating
the end of the bus cycle. B+4 and IOR* out enables HRDY to SD7 so
the status of HRDY may be tested. SD7 is used since the sign bit of a
byte may be easily tested. The rest of the data bits are left floating and
should be ignored. B+8 and IOW* generate a reset pulse which will init
the interface by clearing the two write registers and outputs a reset
pulse, -RS, for the CP chip. The reset instruction is OR'd with RESET
on the bus to initialize the PMD chip set when the PC is reset.
52
53
PWM Motor Interface
Comments on Schematic
The following schematic shows a typical interface circuit between the
MC1241A and an amplifier which accepts an analog curent command
and a separate sign bit.
The A3952 from Allegro Microsystems is an integrated H-bridge
package with internal current loop control which provides all TTL and
power-level circuitry to form a complete amplifier-on-a-chip. The only
other components needed are capacitors and resistors.
The analog current command input to the amplifier chip is constructed
by low pass filtering the digital magnitude output signal from the
chipset. The sign bit is connected directly from the MC1241A chipset to
the amplifier.
The amplifier performs the current control by continuously compariing
the analog input signal from the chipset (current command) to the
measured current and turing on or off the H-bridge drivers accordingly
to maintain the actual current close to the desired current.
Some of the resistor and capacitor values for the circuit may need to be
adjusted depending on the partricular values for the motor resistance
and inductance. In particular the value shown for R7 (.175 Ohm) may
change if a maximum current of less than 2 Amps is desired. Other
values which may be adjusted are R1 and C1. These adjust the overall
PWM frequency (off-time duration) as well as the blanking intervale.
See the Allegro application notes for more information.
54
55
16-Bit Serial DAC Interface
The following schematic shows an interface circuit between the
MC1241A and a dual 16-bit serial DAC
Comments on Schematic
The 16 data bits and the two address bits from the CP chip are latched
in the two 74HC821 latches when the CP writes to address F hex, in
the address bits A0-A3. Three 74HC373 latches could also be used. If
this is a write to the DAC, DACSlct will be asserted during this CPU
cycle. The assertion of DACSlct will be latched by the fed-back and-or
gate, and the next clock will set the DACWR latch. The second clock
will set the second shift flop which will clear the DACL latch. Since this
latch has been cleared the third clock will clear DACWR providing a two
clock DACWR level. The fourth clock will clear the second shift flop
returning the system to its original state waiting for the next DACSlct.
When the DACWR flop is set the 16 bit shift register implemented by
the 2 74FCT299's are parallel loaded with the 16 bits of data for the
DAC. The 4 bit counter, 74FCT161, is also parallel loaded to 0, and the
counter is enabled by clearing the ENP flop, which is contained in half
of the 74HCT109. The counter will not start counting nor the shift
register start shifting until the clock after the DACWR flop clears since
the load overrides the count enable. When the DACWR flop is cleared
the shift register will start shifting and the counter will count the shifts.
After 15 shifts CNT15 from the counter will go high and the next clock
will set the DACLAT flop and clear ENP flop. This will stop the shift after
16 shifts and assert L1 through L4 depending on the address stored in
the latch. The 16th clock also was counted causing the counter to roll
over to 0 and CNT15 to go low. The next clock will therefore clear the
DACLAT flop causing the DAC latch signal L1 through L4 to terminate
and the 16 bits of data to be latched in the addressed DAC. The control
logic is now back in its original state waiting for the next write to the
DACs by the CP.
56
57
NOTES
58
NOTES
59
Internal Block Diagram
Incremental Encoder
Index Home
1/a
Motor Output
B
A
1/a
1/a
PWM sign PWM dir.
1/a
DAC address
2
1/phase
16
PWM, DAC signal generator (2-4 channels)
Microstepping
Generator (2)
Quadrature
decoder
counter (2)
Trajectory
profile generator
Index capture
register (2)
System Registers (2)
Host I/O controller
5
Control
8
Host command
1/a
1
Data
host interrupt
PosLimit
Host I/O
1/a
NegLimit
Over-travel Inputs
Technical Specifications
2 axes with internal microstepping generation (MC1241A)
1 axis with internal microstepping generation (MC1141A)
Open loop (uses trajectory generator, microstep generator)
Operating Modes:
-1,073,741,824 to 1,073,741,823 counts
Position Range:
-16,384 to 16,383 usteps/cycle with a resolution of 1/65,536 usteps/cycle
Velocity Range:
S-curve profile: -1/2 to 1/2 usteps/cycle^2 with a resolution of 1/65,536 usteps/cycle^2
Acceleration Range:
All other profiles: -16,384 to 16,383 usteps/cycle^2 with a resolution of 1/65,536 usteps/cycle^2
-1/2 to 1/2 usteps/cycle^3, with a resolution of 1/4,294,967,296 usteps/cycle^3
Jerk Range:
Trajectory Profile Generator Modes: S-curve (host commands final position, maximum velocity, maximum acceleration, and jerk)
Trapezoidal (host commands final position, maximum velocity, and acceleration)
Velocity contouring (host commands maximum velocity, acceleration)
Electronic Gear (Encoder position used as position command for corresponding stepper axis).
32768:1 to 1:32768 (negative and positive direction)
Electronic Gear Ratio Range:
Sinusoidal
Microstepping Waveform:
64
# Steps Per Full Step:
15 kHz
Microstep lookup rate:
90 degrees (used with 2-phase steppers)
Phasing:
120 degrees (used with 3-phase steppers & AC Induction Motors)
2
# of Output Phases:
8 bits
PWM Resolution:
97.6 kHz
PWM Frequency:
Incremental Encoder Input Signals: A, B, Index
1.75 mCounts/sec
Maximum Encoder Rate:
540 uSec/cycle
Profile Cycle Rate
2 (one for each direction of travel)
# of Limit Switches Per Axis:
Hardware Position Capture Latency: 160 nSec
Hardware Position Capture Triggers: Index signal (quadrature A and B must be low)
Home signal
80
# of Host Commands:
Available Configurations:
Ordering
Information
Chipset
p/n: MC1
41A
2 - 2 axis
1 - 1 axis
Custom chipset versions
also available. Call PMD
Chipset Developer's Kit
p/n: DK1241A*
*(Supports MC1241A and
MC1141A)
Performance Motion Devices, Inc. 12 Waltham St. Lexington, MA 02421 tel: 781.674.9860 fax: 781.674.9861 www.pmdcorp.com