ETC DRM010

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Vacuum Cleaner
Reference Design
Designer Reference
Manual
M68HC08
Microcontrollers
DRM010/D
Rev. 0, 2/2003
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Vacuum Cleaner Reference
Design
Designer Reference Manual — Rev 0
by: Ken Berrenger
Motorola, East Kilbride
DRM010 — Rev 0
Designer Reference Manual
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List of Paragraphs
List of Paragraphs. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
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Table of Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
List of Figures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
List of Tables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Section 1. Vacuum Cleaner Reference Design. . . . . . . . 13
Section 2. Reference Design Code . . . . . . . . . . . . . . . . . 37
Section 3. Revision History . . . . . . . . . . . . . . . . . . . . . . . 59
Section 4. Glossary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
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List of Paragraphs
Designer Reference Manual
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List of Paragraphs
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Table of Contents
List of Paragraphs
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Table of Contents
List of Figures
List of Tables
Section 1. Vacuum Cleaner Reference Design
1.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
1.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
1.3
System Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16
1.4
Phase Angle Control Basics . . . . . . . . . . . . . . . . . . . . . . . . . . .22
1.5
Triac Drive Waveform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24
1.6
Vacuum Software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27
1.7
Input Capture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29
1.8
Output Compare . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30
1.9
Control Loop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30
1.10
Interrupt Timing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31
1.11
Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33
1.12
Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35
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Table of Contents
Section 2. Reference Design Code
2.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37
2.2
Vacuum Cleaner Reference Design Code . . . . . . . . . . . . . . . .37
Section 3. Revision History
3.1
Contents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .59
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3.2
Major Changes From Application Note AN1843/D to DRMxxx/D
Rev 0 59
Section 4. Glossary
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List of Figures
Figure
Title
Page
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Vacuum Cleaner Plus Circuit Board . . . . . . . . . . . . . . . . . . . . . . . . . .15
Vacuum Cleaner Reference Design . . . . . . . . . . . . . . . . . . . . . . . . . .16
HC908KX6 Universal Motor Development System (top). . . . . . . . . . .18
HC908KX6 Universal Motor Development System (bottom). . . . . . . .19
Circuit Board . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20
Vacuum Cleaner Software Development System . . . . . . . . . . . . . . . .21
Phase Angle Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
Continuously Variable Phase Angle . . . . . . . . . . . . . . . . . . . . . . . . . .23
Undesirable Turn Off Using Short Pulse . . . . . . . . . . . . . . . . . . . . . . .25
Triac Pulse at Different Phase Angles. . . . . . . . . . . . . . . . . . . . . . . . .26
Software Flow Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29
CPU Process Timing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33
Hard Start Using an On-Off Switch . . . . . . . . . . . . . . . . . . . . . . . . . . .34
Soft Start Using MCU with Software . . . . . . . . . . . . . . . . . . . . . . . . . .35
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List of Figures
Designer Reference Manual
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List of Tables
Table
Title
Page
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Triac Pulse Generation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27
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Section 1. Vacuum Cleaner Reference Design
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1.1 Contents
1.2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13
1.3
System Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16
1.4
Phase Angle Control Basics . . . . . . . . . . . . . . . . . . . . . . . . . . .24
1.5
Triac Drive Waveform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .24
1.6
Vacuum Software . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27
1.7
Input Capture . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29
1.8
Output Compare . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30
1.9
Control Loop . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30
1.10
Interrupt Timing. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31
1.11
Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .33
1.12
Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35
1.2 Introduction
The modern vacuum cleaner is an indispensable household appliance.
The upright and the canister are the two basic types. The upright is the
most common in the United States and the United Kingdom, while the
canister vacuum is more common on the European continent. Other
kinds of vacuum cleaners — such as small, hand-held vacuums, large,
central vacuums, and industrial, floor care appliances — are not
addressed in this document.
A vacuum cleaner uses a universal motor meaning that the motor can
operate from either an ac or dc supply. It has brushes like a dc
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permanent magnet motor. However, it has a wound stator that is
connected in series with the rotor windings. In dc applications, it is often
called a series wound dc motor. A universal motor is used in vacuum
cleaners because it can operate at very high speeds. Vacuum cleaner
motors operate at speeds up to 30,000 RPMs. The high-speed operation
is necessary to generate a strong suction using a small fan. An induction
motor is limited to speeds below 3600 RPMs.
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Many vacuum cleaners have just a simple on-off switch for the motor
control. The penetration of electronic controls in vacuum cleaners is
higher in Europe and Asia. Most European canister vacuums have a
variable suction power knob or slider. The motor speed is controlled
using a triac with a simple firing control circuit. The firing control circuit
consists of a few discrete components, such as a diac, resistor,
capacitor, and potentiometer.
Today, a few of the more expensive high-end vacuum cleaner models
use microcontrollers (MCU). Microcontrollers are used to provide added
features for these sophisticated models, such as infrared or wired
remote control, status LEDs (light-emitting diode), and automatic suction
control.
In the near future, all vacuum cleaners might include a microcontroller,
since MCUs provide several benefits for the low-end models.
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Introduction
Figure 1-1. Vacuum Cleaner Plus Circuit Board
One of the most important benefits is soft-start. A microcontroller can
provide a soft-start function using a very simple software algorithm that
will minimize the startup current of the vacuum cleaner. The startup
current of a conventional vacuum might be as high as 60 amperes peak.
If the vacuum draws excessive current during startup, this might cause
the line voltage to dip momentarily. This is readily apparent in common
incandescent lighting and is called voltage flicker. With increased
European community regulations, vacuum cleaner manufacturers must
clean up their power quality. Using an MCU with some simple software
will help manufacturers meet the requirements of EN61000-2-3 and
EN61000-3-3. These standards define limits for line harmonics and
voltage flicker.
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1.3 System Design
A simple vacuum cleaner reference design is shown in Figure 1-2, and
a brief description of the circuit operation follows.
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The HC908KX8 is used to generate the triac drive waveform and control
the speed of the motor. A potentiometer is used to vary the speed of the
motor. The MCU reads the potentiometer using one of the
analog-to-digital converter (ADC) port pins. A single port pin is used with
a timer input capture function to measure the ac line frequency and sync
to the ac line. The current injection into the MCU is limited, using a large
value resistor. Four port pins provide sufficient sink current to drive the
triac directly. A charge pump power supply is used to provide power for
the MCU and drive current for the triac. This type of power supply is
useful only up to about 20 mA. The supply current is limited by the size
of the ac line capacitor. A high-voltage non-polar capacitor is needed to
generate the ac current. A low-cost charge pump power supply does not
have sufficient current capability to drive status LEDs. A sensitive gate
triac can be used to minimize triac drive current. However, sensitive gate
triacs have a lower rate of voltage rise equal dv/dt rating and require a
more expensive snubber circuit.
VDD
VDD
MC68HC908KX8
1
VDD
VSS
2
VSS 3
4
5
6
7
8
VSS
PTA1
PTA0
IRQ
PTB0/AD0
PTB1/AD1
PTB2/AD2
PTB3/AD3
VDD
16
15
PTA4
14
PTA3/TCH1
13
PTA2/TCH0
12
PTB4/RxD
11
PTB5/TxD
10
PTB6/OSC1
9
PTB7/OSC2
VDD
+
VSS
Figure 1-2. Vacuum Cleaner Reference Design
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System Design
While this circuit is simple and cost effective, it is difficult to develop and
debug software in this configuration. A circuit has been developed for the
express purpose of developing vacuum cleaner software for the
HC908KX8. This circuit is shown in Figure 1-6.
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A separate isolated supply provides power to the MCU and triac drive.
This provides safe isolation when working with a Motorola modular
development system (MMDS). This allows a safe direct connection from
MMDS to the MCU socket using a flexible cable. The software may be
safely debugged without connecting the triac to the ac mains. An
external oscillator is used when programming or communicating via
monitor mode.
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Figure 1-3. HC908KX6 Universal Motor Development System (top)
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System Design
Figure 1-4. HC908KX6 Universal Motor Development System (bottom)
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Figure 1-5. Vacuum Cleaner Circuit Board
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System Design
U7
MC78L05
D1
MBR160
C14
100 µF
VDD
VDD
J3
+
C8
1.0 µF
R3
Q3
110 Ω
R10
VDD
1.0 kΩ
R22
10 kΩ
U1
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1
2
3
4
5
VDD
6
7
8
R1
10 kΩ
VSS
VSS
VDD
HC908KX8
100 nF
VSS
VSS
VDD
PTA1
PTA4
PTA0
PTA3/TCH1
IRQ
PTA2/TCH0
PTB0/AD0
PTB1/AD1
PTB2/AD2
PTB3/AD3
PTB4/RxD
VSS
16
VDD
15
14
13
R16
R17
220 kΩ 220 kΩ
12
11
10
PTB6/OSC1
9
PTB7/OSC2
PTB5/TxD
J4
R18
10 kΩ
VSS
C3
Q1
MAC12M
Q5
X1
R26
10 kΩ
C5
100 nF
VSS
VSS
VDD
VDD
R7
470 Ω
D3
R24
10 kΩ
S1
C6
100 nF
VSS
S2
VSS
Figure 1-6. Vacuum Cleaner Software Development System
While it is possible to drive the triac directly, an NPN drive circuit has
several advantages. The NPN drive circuit consists of Q3, R3, R10, and
R22 in Figure 1-6. The NPN drive circuit uses only one port pin. Using
the output compare pin of the timer provides accurate
hardware-generated timing. Multiple pins can be manipulated only by
using software and they have a resulting interrupt latency. The NPN
transistor drive also has better EMC (electromagnetic compliance)
robustness than a direct drive solution. The MCU is not exposed to
current injection due to the triac gate drive voltage. The cost of a small
NPN is less than the cost of a good Schottky diode or zener diode that
are commonly used for EMC protection.
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An additional NPN transistor (Q5) is used to provide an accurate zero
voltage crossing detection circuit. The zero voltage crossing circuit
outputs a square wave to the MCU input capture. The NPN provides a
square wave output over a wide range of input voltages. Two or more
resistors in series may be required due to the limited voltage rating of
metal film or chip resistors. A jumper is also included, providing a
convenient connection to a pulse generator for debugging purposes.
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One of the port pins is used to drive an LED. This is used to indicate the
software has synchronized with the ac line to aid with debugging.
1.4 Phase Angle Control Basics
The concept of phase angle control is to apply only a portion of the ac
waveform to the load. This is illustrated in Figure 1-7. Once fired, the
triac will conduct until the next zero crossing. The average voltage is
proportional to the shaded area under the curve. The phase angle is
measured from the trigger point to the next zero crossing. This is also
referred to as the conduction angle or firing angle.
The phase angle is varied continuously and results in a variety of voltage
waveforms. This is illustrated in Figure 1-8. The phase angle control
software should be able to smoothly vary the phase angle to control the
average voltage applied to the load. Rotating the potentiometer should
increase the phase angle and use a larger portion of the sine wave.
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Phase Angle Control Basics
Θ
Figure 1-7. Phase Angle Control
Figure 1-8. Continuously Variable Phase Angle
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This simple control method is sufficient for most universal motors and
other loads. More complex forms of phase angle control compensate for
the inductive load or provide sensorless speed control of a universal
motor. Closed loop speed control might use a PID (proportional integral
derivative) loop or fuzzy logic algorithm. A vacuum cleaner normally
does not require this level of complexity.
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1.5 Triac Drive Waveform
The key task of the phase angle control software is to provide the trigger
pulse for the triac. The software must synchronize to the ac line voltage
and fire the triac at the desired angle. The design of the triac firing pulse
requires some basic knowledge of the operation of triacs.
Triacs are a latching bilateral switching device. When the triac is off, it
will block voltage in both directions. Once a triac has been fired, it will
latch in the on state and continue to conduct until the current decreases
to zero. The current for an ac load naturally crosses zero every half
cycle. Zero current turn off is in fact desirable and minimizes any
inductive kickback voltage. The triac will not latch on until after the
voltage has increased to above its rated latching voltage and the current
has increased to greater than its rated latching current. Once latched,
the triac will stay on until the current has decreased to below the rated
holding current. For these triac specifications, contact ON
Semiconductor at http://www.onsemi.com. The document order number
is MAC12SM/D.
Because the current passes through zero, the triac must be refired every
half cycle. The triac is fired by applying a trigger pulse to the gate
terminal. A negative gate current is desired for most triacs because the
trigger current is much higher using a positive trigger, in particular when
the load voltage is negative. The duration of the trigger pulse must be
long enough for the load current to reach the triac’s rated latching
current. Once the triac has latched, there is no need to continue to
supply trigger current.
The ac line voltage zero crossing is easily measured using a simple
circuit as shown in Figure 1-6. The load current is not so easily
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Triac Drive Waveform
measured. The MCU’s ADC requires a 0- to 5-V analog signal.
Accurately measuring the load current would require a very small value
resistor and an operational amplifier with a low input-offset voltage.
Fortunately, the load current is not really needed for most applications.
Assume that the load current will lag the voltage for most inductive loads.
Vacuum cleaner universal motors are highly inductive.
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When driving an inductive load, the current will lag the voltage. The triac
does not turn off at zero-voltage crossing. It will continue to conduct for
some degrees until the current passes through zero. As the phase angle
is increased, at some point, the current will become continuous. The
triac will be fired just after zero current crossing. As the phase angle is
increased further, approaching 180°, the triac will be fired before current
zero crossing. If a short pulse is used at these angles, the triac will not
conduct over the rest of the cycle, as shown in Figure 1-9. The end result
would be that the motor suddenly slows when the speed is turned all the
way up.
SHORT
PULSE
VOLTAGE
CURRENT
TRIAC TRIAC
FIRED TURNS
EARLY OFF
Figure 1-9. Undesirable Turn Off Using Short Pulse
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This potential problem can be remedied by extending the triac pulse as
the phase angle approaches 180°. Extending the triac pulse out to about
135° will accommodate inductive loads with a current phase angle up to
45°. This is suitable for most applications.
Extending the triac pulse is illustrated in Figure 1-10.
0°
10°
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20°
30°
40°
50°
60°
70°
80°
90°
100°
110°
120°
130°
140°
150°
160°
170°
180°
Figure 1-10. Triac Pulse at Different Phase Angles
Zero degrees and 180° also require special attention. At zero speed, the
desired output is zero voltage and the triac should not be fired. Firing the
triac at zero degrees would give full speed operation. If the desired
phase angle is too small, the triac should also not be fired. If the triac
pulse were to overlap the next voltage zero crossing, the voltage would
jump from 0 to 100 percent, resulting in an undesirable plugging of the
motor.
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However, small phase angles are needed in some applications. A
vacuum cleaner universal motor has a very low impedance when the
rotor is not moving. If the initial voltage is too high, a high current surge
will result. Experiments have shown that a minimum phase angle of
about 5° is low enough to provide smooth starting. This is essential to
minimize the startup surge current.
Because the current is lagging the voltage, full speed will occur before
180°. The last few degrees do not provide any variation in the motor
speed. It is not crucial to go all the way to the zero crossing. Some delay
between the zero crossing and triac firing is generally acceptable for
inductive loads.
The desired triac firing pattern is summarized in the Table 1-1.
Table 1-1. Triac Pulse Generation
Phase Angle
Action
0° < φ < 5°
None
5° < φ < 135°°
Short pulse at φ
135° φ < 175°
Turn on at φ; turn off at 135°
φ > 135°
Turn on ASAP; turn off at 135°
1.6 Vacuum Software
Software has been developed for basic vacuum cleaner universal motor
control. This software was developed for the HC908KX8. The software
will run on any HC08 MCU that has at least a 2-channel timer and an
ADC. The HC908KX8 also features an internal oscillator and a small
16-pin package. The software is compatible with the internal oscillator or
other low-cost RC oscillators.
The 2-channel timer provides all the necessary timing control for the
software. One channel is used for an input capture to measure the ac
line zero crossing. The second channel is configured as an output
compare and is used to control the timing of the triac pulse.
The software is written in C language. There are numerous advantages
to programming in C, even for small microcontrollers. For instance, the
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HC08 has stack manipulation instructions that permit the C compiler to
effectively use local variables and minimize the RAM requirements. The
HC08 also provides very good code efficiency due to the short
instruction length. The HC908KX8 has eight Kbytes of FLASH memory,
more than enough for a small program. The phase angle control
software takes only about 1.2 Kbytes of program memory. Even a small
1.5-k part might be programmed in C if no complex math or library
functions are included. For this project, the HIWARE C compiler was
used to produce compact code comparable in code size to a hand-coded
assembler in many instances.
The software can be organized in several different ways. For example,
the code could be written as a straightforward procedure using polling.
When using polling, the software would test or poll the zero crossing pin
and wait for a zero crossing. This is the preferred method when using a
small HC05 MCU with limited peripherals. Using an HC08 with a
2-channel timer, the software can be written using interrupts. This
provides more time for the CPU to perform other functions.
Once the MCU has been initialized, all processing could be done in
interrupt service routines. This is a common method of organizing
software. The main procedure would end with a while(1) statement and
all processing is handled by the ISRs (interrupt service routine).
The zero crossing and triac pulses are time critical events and are best
handled by the hardware timers and serviced using interrupts. Other
functions are not time critical and could be performed anywhere in the ac
cycle.
The control loop functions such as reading the ADC, scaling, integrating,
and saturation are not time critical. These functions can be placed in the
main loop. The interrupt service routines will interrupt the calculations as
needed. A mechanism is then needed to synchronize these functions to
the ac line. A sync flag is used for this purpose. The main loop will wait
for the sync flag before updating the phase. The input capture routine will
set the sync flag, enabling the main loop functions. The main loop will
then update the phase information and clear the sync flag.
The resulting flowchart is shown in Figure 1-11. This is a combined
flowchart and state diagram.
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Input Capture
Once the MCU is initialized, the main loop may be interrupted by the
input capture and the output compare interrupt service routines.
START
Freescale Semiconductor, Inc...
INITIALIZE
INTERRUPT
IS SYNC = 1?
InputCapture
NO
SCHEDULES
TRIAC PULSE
SET SYNC = 1
YES
ControlLoop
INTERRUPT
OutputCompare
SET SYNC = 0
GENERATES
TRIAC
PULSE
Figure 1-11. Software Flow Diagram
1.7 Input Capture
The input capture interrupt service routine is executed every time the
input capture timer channel detects an edge on the zero crossing input.
The input capture time is read from the timer channel. The average
period is calculated over two cycles. This value is used as criteria for
locking on the input line frequency. The minimum and maximum periods
are set up to lock from 30 Hz to 90 Hz. This will accommodate both 50and 60-Hz possibilities and up to 50 percent error in the clock frequency.
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An LED is used for debugging to indicate when the software has locked
onto the line frequency.
Freescale Semiconductor, Inc...
The triac pulses are scheduled by the input capture interrupt service
routine.
•
If the phase is less than 5°, the triac is not pulsed.
•
If the phase is less than 135°, a short pulse is used.
•
If the phase is greater than 135°, a long pulse is used.
The pulse function calculates the desired rising and falling edges for
each case. The long pulse function also checks the current time. If the
desired time has already expired, the rising edge will be scheduled as
soon as possible (ASAP). The input capture function sets up the output
compare to generate the rising edge. The time for the falling edge is
calculated and saved for use by the output compare function.
1.8 Output Compare
The output compare interrupt service routine is called for both rising and
falling edges of the triac pulse. The output compare fires the triac and
also turns off the gate pulse at the pre-determined time. If the output
compare was called as a result of the output compare being set high, the
low edge will be scheduled using the saved off time. Otherwise, the
output compare will be disabled.
This method of using the output compare to schedule subsequent output
compares is extremely powerful. Using software, the output compare
can be used to generate practically any desired series of pulses. Once
initiated, the output compare can generate these pulses autonomously.
1.9 Control Loop
The control loop function provides the basic motor control features.
First, the potentiometer is read using the ADC. This takes some time and
program execution will wait until the conversion complete flag has been
set. The analog-to-digital reading is from 0 to 255. The ADC also has
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Interrupt Timing
some uncertainty. The bottom and top range of the potentiometer setting
should provide zero and full-speed operation. Saturation is provided to
compensate for this requirement.
Freescale Semiconductor, Inc...
The ADC value is scaled to obtain the desired 0° to 180° range. The ADC
reading is multiplied by 180, then divided by 255. The HC08 is capable
of performing an 8 by 8 multiply and a 16 by 8 divide efficiently. Inline
assembler functions are used to access the HC08 math functions
directly, resulting in fast and efficient code. Most ANSI C compilers
(American Standard Code for Information Exchange) will promote both
operands to 16-bit integers before performing a multiply or divide. This
results in inefficient code when using 8-bit unsigned char variables.
An integral controller is used to provide soft-starting and a smooth ramp
in the motor speed. Slowly, the controller will increment the output phase
until it reaches the desired speed setting. This will limit the motor current
during starting. When the desired speed is modified by changing the
potentiometer setting, the speed will smoothly ramp to the new setting.
The integrate function provides a simple integral controller. The
integrator output is stored in a static variable called PhaseI. This variable
is incremented or decremented depending on the input variable. The
integrator update rate determines how fast the integrator will ramp the
output.
The saturate function compensates for the characteristics of the
potentiometer and the desired output phase. If the input is less than 5°,
the output will be rounded down to 0°. If the input is greater than 175°, it
will be rounded up to 180°. The saturation is placed after the integrator
to provide saturation to the output phase.
1.10 Interrupt Timing
The input capture always occurs at the zero crossing. Normally, the
MCU should be idle at this time. The timing of the output compare
interrupt service routine is variable and depends on the phase angle and
the width of the triac pulse. If the phase angle is small, a short pulse is
used, and the output compare function is called twice in rapid
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succession. The triac pulse must be large enough to account for the
interrupt latency of the output compare function.
If the phase angle is larger than 135°, the output compare will be called
first at the phase angle and then a second time at 135°. There is an idle
period between the output compare interrupts.
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The control loop function is normally executed after the input capture
function. However, when the triac phase angle aproaches its maximum
of 180°, the output compare interrupt service routine will pre-empt the
control loop. The time of the interrupt service routines is shown in
Figure 1-12.
The MCU is idle for most of the ac cycle. The time critical operations
occur immediately after zero crossing. The execution time of the input
capture routine will determine the maximum phase angle. A maximum
phase angle of 175° is perfectly acceptable for an inductive load like the
vacuum cleaner motor.
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Results
120°
135°
150°
165°
175°
inputCapture
controlLoop
outputCompare
idle
Figure 1-12. CPU Process Timing
1.11 Results
The software was first tested using a modular microcontroller
development system (MMDS), bus state analyzer, pulse generator, and
digital oscilloscope. The pulse generator was used to simulate the ac
line and test the lock range of the software. The digital storage scope
was used to examine the triac pulse waveform in relation to the pulse
generator. The first few pulses are critical to the startup operation. It is
important that there be no errant pulses. The pulses also should change
smoothly without any glitches.
Once fully satisfied with the operation of the software, a FLASH device
was programmed and inserted in the socket. The test board was
connected to a vacuum cleaner motor and an ac variac and safety
isolation transformer. Bringing the ac line up slowly will minimize the
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chance of catastrophic failures due to wiring or software errors. Later,
the system was tested for hard-starts using an on-off switch directly off
a stiff ac source.
After debugging, the software provided good results. A startup delay was
added to prevent errant pulses during startup. The integrator rate was
adjusted to provide a ramp time of about three seconds from zero to full
speed. This provided a smooth soft-start and a good feel to the speed
control.
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The startup current of the vacuum cleaner motor was measured using a
simple on-off switch shown in Figure 1-13. The peak current was about
40 amps. The startup current was measured using the same motor with
the electronic soft-start shown in Figure 1-14. The peak current was less
than 20 amps. The performance is better than the numbers indicate. In
fact, the MCU controlled motor did not exhibit a startup surge at all. The
peak current occurs when the motor reaches maximum speed.
Figure 1-13. Hard Start Using an On-Off Switch
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Conclusions
Figure 1-14. Soft Start Using MCU with Software
The soft-start feature effectively eliminates any startup surge. The
software provides robust control of a universal motor over a wide range
of conditions. The software is compact, efficient, and suitable for any
HC08 microcontroller.
1.12 Conclusions
A cost-effective microprocessor-based system has been developed to
provide phase angle control for vacuum cleaners. Software has been
developed to provide phase angle control with a soft-start feature. This
solution has proven to dramatically reduce the startup current. The
reduction in startup current is essential to meet increasingly stringent
power quality requirements in Europe.
The basic requirements on phase angle control and triac drive have
been discussed. The software provides optimum pulse generation for
driving inductive loads. The pulse width is lengthened for large phase
angles.
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The 8-bit microcontroller chosen, the Motorola HC908KX8, provides all
of the required features in a small 16-pin package. This internal oscillator
eliminates the need for an external crystal or RC oscillator. This device
is well suited for vacuum cleaners and other small appliances.
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The basic software coded in C, when compiled, only uses about
1200 bytes of program memory. This leaves about 7000 bytes of
program memory available for additional functions. The C code listing is
included in this application note and follows the main text. The
interrupt-driven software uses less than 10 percent of the total available
CPU (central processor unit) load running at 4 MHz. This frees the CPU
for other tasks. Additional functions can be implemented in the
foreground with good performance virtually unimpeded by interrupt
processing. The software is flexible and reusable for a variety of phase
angle control applications.
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Section 2. Reference Design Code
2.1 Contents
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2.2
Vacuum Cleaner Reference Design Code . . . . . . . . . . . . . . . .37
2.2 Vacuum Cleaner Reference Design Code
/*****************************************************************************
Copyright (c) Motorola 1999
File Name
: vacuum.c
Engineer
:
Ken Berringer
Location
:
EKB
Date Created
: 1 Dec 1999
Current Revision :
1.0
Notes:
This is the code for the vacuum cleaner reference design. The code
includes detailed comments before each function. The code is
organized in a single C file. There are two included header files,
one for the standard HC08KX8 register definitions "hc08kx6.h" and
a second application specific header file for the vacuum code
"vacuum.h". All of the function prototypes and constants are in
the vacuum.h header file.
Most of the code is in high level C code. Hardware driver
functions are in low level C or inline assembler.
*****************************************************************************/
#include "hc08kx6.h"
#include "vacuum.h"
/****************************************************************************
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global variables
The following variables are defined as global. These are used and
modified by both the main loop and the interrupt service routines.
There are manually initialized and don't depend on the startup
code.
Freescale Semiconductor, Inc...
****************************************************************************/
unsigned
unsigned
unsigned
unsigned
char Phase;
int Degrees;
char Sync;
int OffTime;
/****************************************************************************
Global Variables (could be static)
The following variables are defined as global. They are only used
in specific functions and could also be declared as static. Global
variables are more useful for debugging. The contents of global
variables are listed in the debugger, static variables are not
listed until the function is entered. These variables are also
initialized manually by the init function.
****************************************************************************/
unsigned char Update;
unsigned char PhaseI;
unsigned int Period[2];
unsigned char Cycle;
unsigned int Told;
signed char ModError;
/******************************************************************************
function
:
main()
parameters
:
void
returns
:
void
type
:
main
Description:
The main code is very simple. It initializes everything, then
calls a startup delay. The endless while(1) loop will wait until
after the input capture sets the sync flag. Then it update the
phase angle and reset the flag.
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*******************************************************************************/
void main (void)
{
init();
startupDelay(8);
while(1)
{
while(!Sync);
Phase = controlLoop();
Sync=0;
}
}
/******************************************************************************
function
:
init()
parameters
:
void
returns
:
void
type
:
normal
Description:
The init function clears all global variables explicitly. This
allows one to eliminate the startup code. It then initializes the
timer, enables the input capture, and enables interrupts.
*******************************************************************************/
void init (void)
{
initMCU();
unsigned char Phase=0;
Phase=0;
Degrees=0;
Told=0;
Period[0]=0;
Period[1]=0;
Cycle=0;
Update=0;
ModError = 0;
Sync=0;
OffTime=0;
initTimer();
enableIC();
ENABLE_INTERUPTS;
}
/******************************************************************************
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Reference Design Code
function
:
startupDelay()
parameters
:
unsigned char i - delay count, zero crossings
returns
:
void
type
:
normal re-entrant
Description:
The startupDelay() function is provided to ensure that the
everything is stable before starting the motor. This prevents
errant pulses which might result in a high surge currents. The
Phase angle will remain at zero until the startupDelay is
completed.
*******************************************************************************/
void startupDelay(unsigned char i)
{
unsigned char j;
for (j=0;j<i;j++)
{
while(!Sync);
Sync=0;
}
}
/******************************************************************************
function
:
controlLoop()
parameters
:
void
returns
:
void
type
:
normal re-entrant
Description:
The controlLoop function is executed after each zero crossing.
This function reads the pot updates the phase angle. Scaling
integration and saturation are implemented in this function.
A more complex PID loop or fuzzy logic block could also be
implemented here. The function is executed with interrupts
enabled and might be interrupted by the output compare function.
*******************************************************************************/
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unsigned char controlLoop(void)
{
unsigned char x;
x = readPot();
x = scale (x);
x = integrate(x);
x = saturate(x);
return x;
}
Freescale Semiconductor, Inc...
/******************************************************************************
function
:
scale()
parameters
:
unsigned char x - input from the A/D
returns
:
unsigned char x - scaled output
type
:
normal re-entrant
Description:
The scale function will scale the A/D measurement (0-255) to
degrees (0-180). The number is first multiplied by 180, then
divided by 255. The mul() and div() functions are optimized for
HC08 8-bit math.
*******************************************************************************/
unsigned char scale(unsigned char x)
{
unsigned int y;
y = mul(180,x);
x = div(y,255);
return x;
}
/******************************************************************************
function
:
integrate()
parameters
:
unsigned char x - input
returns
:
unsigned char x - output
type
:
normal re-entrant
Description:
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The integrate function provides a simple integral controller to
provide a smooth ramp to the phase output. The UPDATE_RATE sets
the rate at which the integrator output is incremented. Update and
PhaseI could be global or static.
*******************************************************************************/
unsigned char integrate(unsigned char x)
{
Freescale Semiconductor, Inc...
Update++;
if(Update==UPDATE_RATE)
{
Update = 0;
if (x > PhaseI)
{
PhaseI++;
}
else if (x < PhaseI)
{
PhaseI--;
}
}
return PhaseI;
}
/******************************************************************************
function
:
saturate()
parameters
:
unsigned char x - input
returns
:
unsigned char x - output
type
:
normal re-entrant
Description:
This function provides saturation for the output phase. If the
phase is greater than 175 or less than 5, it is rounded up or down
respectively.
*******************************************************************************/
unsigned char saturate(unsigned char x)
{
if (x < 5)
{
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x = 0;
}
else if (x > 175)
{
x = 180;
}
return x;
}
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/******************************************************************************
function
:
inputCapture()
parameters
:
void
returns
:
void
type
:
interrupt service routine
Description:
This function is called every time a zero crossing occurs. It
reads the input capture register and calculates the average
period. It the average period is within acceptable range, it will
pulse the triac. The Sync flag is then set to allow the phase to
be updated and the input capture is reset. If the average period
is not within the acceptable value the input capture will be
ignored.
*******************************************************************************/
void debugIC(void);
#pragma TRAP_PROC
void inputCapture(void)
{
unsigned int t, pAvg;
t = readIC();
pAvg=calcpAvg(t);
if (pAvg > MIN_PER && pAvg < MAX_PER)
{
updateDegrees();
pulseTriac(t);
Sync=1;
LED=LIT;
}
else
{
LED=DIM;
}
resetIC();
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}
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/******************************************************************************
function
:
calcpAvg()
parameters
:
unsigned int t - input capture time
returns
:
unsigned int pAvg - average period
type
:
normal (called by ISR)
Description:
This function calculates the average period over two cycles.
The period is saved for the last two periods in an array.
The array index Cycle is flipped after storing the current period.
It will take two good input captures before the average period
can be accurately calculated.
*******************************************************************************/
unsigned int calcpAvg(unsigned int t)
{
unsigned int avg;
Period[Cycle] = t - Told;
Told = t;
Cycle = (Cycle + 1) & 0x01;
avg = (Period[0] + Period[1])>>1;
return avg;
}
/******************************************************************************
function
:
updateDegrees()
parameters
:
void
returns
:
void
type
:
normal (called by ISR)
Description:
This function updates the base unit Degrees. The function
is called after flipping the Cycle index. Thus, the value
for degrees will be calculated using the previous period.
This compensates for any waveform asymmetry. It uses a hardware
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divide function div() to avoid the slow ANSI c implementation.
*******************************************************************************/
void updateDegrees(void)
{
Degrees = div(Period[Cycle],180);
}
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/******************************************************************************
function
:
pulseTriac()
parameters
:
unsigned int t - input capture time
returns
:
void
type
:
normal (called by ISR)
Description:
This function will schedule the triac output pulses.
There are four different cases. The output compares
are scheduled differently depending on the output
Phase.
*******************************************************************************/
void pulseTriac(unsigned int t)
{
if (Phase <5)
{
noPulse();
}
else if (Phase <135)
{
shortPulse(t);
}
else
{
longPulse(t);
}
}
/******************************************************************************
function
:
noPulse()
parameters
:
void
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returns
:
void
type
:
normal (called by ISR)
Description:
This function does not pulse the output triac.
Freescale Semiconductor, Inc...
*******************************************************************************/
void noPulse (void)
{
}
/******************************************************************************
function
:
shortPulse()
parameters
:
unsigned int t - input capture time
returns
:
void
type
:
normal (called by ISR)
Description:
This function generates a short pulse at the desired
phase angle. the onTime and OffTime are calculated.
The output compare is initializes to set the pin high
on the next match. The OffTime is a global variable.
The outputCompare will use the OffTime to set
up the next edge.
*******************************************************************************/
void shortPulse (unsigned int t)
{
unsigned int onTime;
onTime = t + mul((180-Phase),Degrees);
OffTime = onTime + mul(2,Degrees);
scheduleHigh(onTime);
}
/******************************************************************************
function
:
longPulse()
parameters
:
unsigned int t - input capture time
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returns
:
void
type
:
normal (called by ISR)
Description:
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This function generates a long pulse at the desired phase angle.
The OffTime is extended out to 45 degrees. This will ensure the
triac will not turn off prematurely, even if the current is lagging
by up to 45 degrees.
*******************************************************************************/
void longPulse (unsigned int t)
{
unsigned int onTime, asap;
onTime = t + mul((180-Phase),Degrees);
OffTime = t + mul(47,Degrees);
asap = readTCNT() + LATENCY;
if (onTime>asap)
{
scheduleHigh(onTime);
}
else
{
scheduleHigh(asap);
}
}
/******************************************************************************
function
:
outputCompare()
parameters
:
void
returns
:
void
type
:
Interupt Service Routine
Description:
This function is called on an output compare. If the output compare
was set to last set the OC high then the falling edge is scheduled
using OffTime. Otherwise the output compare function is disabled.
*******************************************************************************/
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#pragma TRAP_PROC
void outputCompare (void)
{
if (OC_WAS_SET_HIGH)
{
scheduleLow(OffTime);
}
else
{
disableOC();
}
}
/******************************************************************************
function
:
initMCU()
parameters
:
void
returns
:
void
type
: low level c
description:
This function initializes the MCU config registers, clock, ports,
and ADC.
*******************************************************************************/
void initMCU(void)
{
unsigned char i,j;
CONFIG2=0x08;
CONFIG1=0x31;
ICGMR = 0x15;
/*External Clock on pin 6, Pin 7 GP I/O, rev0.7*/
/*LVI reset disabled, LVI power disabled, COP disabled*/
/*init ICGMR to default setting*/
for(i=255;i!=0;i--)
{
ICGCR = 0x13;
for(j=255;j!=0;j--);
if(ICGCR==0x13)break;
}
/*try 256 times*/
ADCLK=0x60;
/*xclk / 8 for 8 MHz xtal*/
PTA3=0;
DDRA = 0x08;
PTA3=0;
/*triac is off*/
/*PTA2/TCH0 is IC, PTA3/TACH1 is output */
/*triac is off*/
/*switch to ext clock*/
/*wait*/
/*test*/
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PTB4=1;
DDRB = 0x10;
PTB4=1;
/* LED off (high) */
/* PTB4 LED output */
/* LED off (high) */
}
Freescale Semiconductor, Inc...
/******************************************************************************
function
:
initTimer()
parameters
:
void
returns
:
void
type
: low level c
description:
This function initializes the timer
*******************************************************************************/
void initTimer(void)
{
TSC = 0x01;
TMODH = 0xff;
TMODL = 0xff;
TSC1= PRESET_LOW;
/*TIM CLK = bus clock/2 (2.4576 MHz/2 )*/
/*set modulus register*/
/*set modulus register*/
}
/******************************************************************************
function
:
readPot()
parameters
:
void
returns
:
unsigned char ADR
type
: low level c
description:
This function reads the ADC ch3 and returns the value. It uses polling
and will wait until a conversion is complete.
*******************************************************************************/
unsigned char readPot(void)
{
ADSCR=0x03;
/* select channel 3 */
while((ADSCR & 0x80)==0x00);
/* wait for COCO bit */
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return (ADR);
}
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/******************************************************************************
function
:
scheduleHigh()
parameters
:
unsigned int i - set high time
returns
:
void
type
:
inline assembler
description:
This function initializes the output compare to set the pin high
at the specified time. It uses inline assembler to ensure the
timer control register is accessed properly.
*******************************************************************************/
void scheduleHigh(unsigned int i)
{
asm
{
lda TSC1_;
ora #0x4c; /*set CH1IE, ELSxA, ELSxB*/
and #0x7f; /*clear CH1F*/
sta TSC1_;
lda i:0;
sta TCH1H_;
lda i:1;
sta TCH1L_;
}
}
/******************************************************************************
function
:
scheduleLow()
parameters
:
unsigned int i - set low time
returns
:
void
type
:
inline assembler
description:
This function initialize the output compare to set the pin low
at the specified time. It uses inline assembler to ensure the
timer control register is accessed properly.
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*******************************************************************************/
void scheduleLow(unsigned int i)
{
asm
{
lda TSC1_;
ora #0x48; /* set CH1IE, set ELSxB*/
and #0x7b; /* clear CH1F, clear ELSxA, */
sta TSC1_;
lda i:0;
sta TCH1H_;
lda i:1;
sta TCH1L_;
}
}
/******************************************************************************
function
:
disableOC()
parameters
:
void
returns
:
void
type
: inline assembler
description:
This function will disable the timer output compare function. It will
disable further interupts and disable output compares by reading
the high byte only.
*******************************************************************************/
void disableOC(void)
{
asm
{
lda TSC1_;
and #0xb3; /clear CHIE, ELSA, ELSB*/
sta TSC1_;
lda TCH1H_;
}
}
/******************************************************************************
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function
:
enableIC()
parameters
:
void
returns
:
void
type
: low level c
Freescale Semiconductor, Inc...
description:
This function will enable the timer input capture function. It uses a three
step process to set up the timer status and control register.
*******************************************************************************/
void enableIC(void)
{
TSC0 = 0x04;
TSC0 &= ~BIT7;
TSC0 |= BIT6;
}
/* input capture mode, rising edges */
/*clear flag*/
/*enable ints*/
/******************************************************************************
function
:
resetIC()
parameters
:
void
returns
:
void
type
: low level c and assembler
description:
This function will reset the timer input capture function. It will
access the TSCO, complement the edge trigger bits, and clear the flag.
*******************************************************************************/
void resetIC()
{
asm lda TSC0_;
/*access TSC0*/
TSC0 ^= 0x0c;
/*flip edge*/
TSC0 &= ~BIT7;
/*clear flag*/
}
/******************************************************************************
function
:
readIC()
parameters
:
void
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returns
:
unsigned int time (in X:A)
type
: inline assembler, no entry or exit
description:
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This function read the input capture time from the timer channel.
The entire function is in assembler. It is necessary to read the
timer channels in the specified order. The function returns the
sixteen bit value.
This function depends on the compiler returning the value in the
X:A register. It will generate return value expected warning
because the return value is not specified in C syntax.
This function could also be coded as below. This version will not
generate a warning and might work on other compilers. However, it
will triple the code size of this function.
unsigned int readIC(void)
{
unsigned int m;
asm {
ldx TCH0H_;
sta m:1;
lda TCH0L_;
sta m:0;
}
return m;
}
*******************************************************************************/
#pragma NO_ENTRY
#pragma NO_EXIT
#pragma NO_FRAME
unsigned int readIC(void)
{
asm {
ldx TCH0H_;
lda TCH0L_;
rts;
}
}
/******************************************************************************
function
:
readTCNT()
parameters
:
void
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returns
:
unsigned int time (in X:A)
type
: inline assembler, no entry or exit
description:
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This function read the time from the timer counter.
The entire function is in assembler. It is necessary to read the
timer channels in the specified order. The function returns the
sixteen bit value.
This function depends on the compiler returning the value in the
X:A register. It will generate return value expected warning
because the return value is not specified in C syntax.
*******************************************************************************/
#pragma NO_ENTRY
#pragma NO_EXIT
#pragma NO_FRAME
unsigned int readTCNT(void)
{
asm {
ldx TCNTH_;
lda TCNTL_;
rts;
}
}
/******************************************************************************
function
:
mul()
parameters
:
unsigned char x,y (in X and A)
returns
:
unsigned int z (in X:A)
type
: inline assembler, no entry or exit
description:
This function will multiply two 8 bit numbers together and return
a sixteen bit value. It is coded entirely in assembler and is very
efficient (two bytes!).
This function is used to provide an efficient 8 x 8 multiply. An
ANSI standard C compiler would normally promote two unsigned char
to unsigned ints before multiplication, resulting in inefficient
code.
*******************************************************************************/
#pragma NO_ENTRY
#pragma NO_EXIT
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#pragma NO_FRAME
unsigned int mul(unsigned char x, unsigned char y)
{
asm {
mul;
rts;
}
}
/******************************************************************************
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function
:
div()
parameters :
unsigned int dvnd, unsigned char dvsr
returns
:
unsigned char dvsr (used for quotient)
type
: inline assembler, no entry or exit
description:
This function provides a hardware 16x8 divide function.
Standard ANSI c will promote everything to a int before
dividing. This is much faster.
*******************************************************************************/
unsigned char div(unsigned int dvnd, unsigned char dvsr)
{
asm {
lda dvnd:0;
psha;
pulh;
lda dvnd:1;
ldx dvsr;
div;
sta dvsr;
}
return dvsr;
}
/******************************************************************************
function
:
shift8()
parameters
:
unsigned int x (in X:A)
returns
:
unsigned int z (in X:A)
type
: inline assembler, no entry or exit
description:
This function will divide a 16 bit number by 256 and return an 8
bit number. It is coded entirely in assembler and is very efficient
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(3 bytes!).
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This function is used to provide an efficient byte shift. The
Hiware compiler will perform a sixteen bit shift 8 times.
*******************************************************************************/
#pragma NO_ENTRY
#pragma NO_EXIT
#pragma NO_FRAME
unsigned char shift8(unsigned int x)
{
asm {
txa;
clrx;
rts;
}
}
/******************************************************************************
function
:
unusedVector()
parameters
:
void
returns
:
void
type
: interrupt service routine
description:
This function provides a mechanism for unusedVectors for the HC08.
*******************************************************************************/
#pragma TRAP_PROC
void unusedVector(void)
{
}
/****************************************************************************
Copyright (c) Motorola 1999
File Name
: vacuum.h
Engineer
:
Ken Berringer
Location
:
EKB
Date Created
: 1 Dec 1999
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Current Revision :
Notes
1.0
:
This header file contains constant definitions, macro definitions,
and function prototypes for the vacuum software.
*****************************************************************************
Freescale Semiconductor, Inc...
constant definitions
*****************************************************************************/
#define ON 1
#define OFF 0
#define LED PTB4
#define LIT 0
#define DIM 1
#define MAX_PER (unsigned int)(300000/30)
#define MIN_PER (unsigned int)(300000/90)
#define UPDATE_RATE 2
#define LATENCY 48
#define UPPER_LIMIT 105
#define LOWER_LIMIT 75
#define NOTCH (UPPER_LIMIT - LOWER_LIMIT)
/****************************************************************************
macro definitions
*****************************************************************************/
#define
#define
#define
#define
#define
#define
#define
#define
OC_WAS_SET_HIGH (TSC1 & 0x0c)==0x0c
PRESET_LOW
0x10
PRESET_HIGH
0x00
SET_ON_OC
0x1c
CLEAR_ON_OC
0x18
SET_CHIE
asm BSET 6,TSC1_
CLR_CHIE
asm BCLR 6,TSC1_
ENABLE_INTERUPTS asm cli
/****************************************************************************
KX8 register defs
These definitions are used for the inline assembler functions.
*****************************************************************************/
#define TCNTH_ 0x21
#define TCNTL_ 0x22
#define TSC0_ 0x25
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#define
#define
#define
#define
#define
TCH0H_
TCH0L_
TSC1_
TCH1H_
TCH1L_
0x26
0x27
0x28
0x29
0x2A
/****************************************************************************
Freescale Semiconductor, Inc...
function prototypes
*****************************************************************************/
void main(void);
void init(void);
void startupDelay(unsigned char);
unsigned char controlLoop(void);
unsigned char scale(unsigned char);
unsigned char integrate(unsigned char);
unsigned char modulate(unsigned char);
unsigned char saturate(unsigned char);
void inputCapture(void);
void updateDegrees(void);
unsigned int calcpAvg(unsigned int);
void pulseTriac(unsigned int);
void noPulse(void);
void shortPulse(unsigned int);
void longPulse(unsigned int);
void maxPulse(unsigned int);
void outputCompare(void);
void initMCU(void);
void initTimer(void);
unsigned char readPot(void);
void enableIC(void);
unsigned int readIC(void);
void resetIC(void);
void scheduleHigh(unsigned int i);
void scheduleLow(unsigned int i);
void disableOC(void);
unsigned int readTCNT(void);
unsigned int mul(unsigned char, unsigned char);
unsigned char shift8(unsigned int);
unsigned char div(unsigned int, unsigned char);
/****************************************************************************/
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Designer Reference Manual — DRM010
Section 3. Revision History
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3.1 Contents
3.2
Major Changes From Application Note AN1843/D to DRM010/D
Rev 0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .59
3.2 Major Changes From Application Note AN1843/D to DRM010/D Rev 0
Reformatted in new template and renamed as a Designer Reference
Manual.
Section
Page (in
DRMxxx/D Rev 0)
1
15, 18, 19 and 20
Description of change
Addition of Figure 1-1, Figure 1-3, Figure 1-4 and Figure 1-5
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Revision History
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Section 4. Glossary
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A — See “accumulators (A and B or D).”
accumulators (A and B or D) — Two 8-bit (A and B) or one 16-bit (D) general-purpose registers
in the CPU. The CPU uses the accumulators to hold operands and results of arithmetic
and logic operations.
acquisition mode — A mode of PLL operation with large loop bandwidth. Also see ’tracking
mode’.
address bus — The set of wires that the CPU or DMA uses to read and write memory locations.
addressing mode — The way that the CPU determines the operand address for an instruction.
The M68HC12 CPU has 15 addressing modes.
ALU — See “arithmetic logic unit (ALU).”
analogue-to-digital converter (ATD) — The ATD module is an 8-channel, multiplexed-input
successive-approximation analog-to-digital converter.
arithmetic logic unit (ALU) — The portion of the CPU that contains the logic circuitry to perform
arithmetic, logic, and manipulation operations on operands.
asynchronous — Refers to logic circuits and operations that are not synchronized by a common
reference signal.
ATD — See “analogue-to-digital converter”.
B — See “accumulators (A and B or D).”
baud rate — The total number of bits transmitted per unit of time.
BCD — See “binary-coded decimal (BCD).”
binary — Relating to the base 2 number system.
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binary number system — The base 2 number system, having two digits, 0 and 1. Binary
arithmetic is convenient in digital circuit design because digital circuits have two
permissible voltage levels, low and high. The binary digits 0 and 1 can be interpreted to
correspond to the two digital voltage levels.
binary-coded decimal (BCD) — A notation that uses 4-bit binary numbers to represent the 10
decimal digits and that retains the same positional structure of a decimal number. For
example,
Freescale Semiconductor, Inc...
234 (decimal) = 0010 0011 0100 (BCD)
bit — A binary digit. A bit has a value of either logic 0 or logic 1.
branch instruction — An instruction that causes the CPU to continue processing at a memory
location other than the next sequential address.
break module — The break module allows software to halt program execution at a
programmable point in order to enter a background routine.
breakpoint — A number written into the break address registers of the break module. When a
number appears on the internal address bus that is the same as the number in the break
address registers, the CPU executes the software interrupt instruction (SWI).
break interrupt — A software interrupt caused by the appearance on the internal address bus
of the same value that is written in the break address registers.
bus — A set of wires that transfers logic signals.
bus clock — See "CPU clock".
byte — A set of eight bits.
CAN — See "Motorola scalable CAN."
CCR — See “condition code register.”
central processor unit (CPU) — The primary functioning unit of any computer system. The
CPU controls the execution of instructions.
CGM — See “clock generator module (CGM).”
clear — To change a bit from logic 1 to logic 0; the opposite of set.
clock — A square wave signal used to synchronize events in a computer.
clock generator module (CGM) — The CGM module generates a base clock signal from which
the system clocks are derived. The CGM may include a crystal oscillator circuit and/or
phase-locked loop (PLL) circuit.
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Glossary
comparator — A device that compares the magnitude of two inputs. A digital comparator defines
the equality or relative differences between two binary numbers.
computer operating properly module (COP) — A counter module that resets the MCU if
allowed to overflow.
condition code register (CCR) — An 8-bit register in the CPU that contains the interrupt mask
bit and five bits that indicate the results of the instruction just executed.
Freescale Semiconductor, Inc...
control bit — One bit of a register manipulated by software to control the operation of the
module.
control unit — One of two major units of the CPU. The control unit contains logic functions that
synchronize the machine and direct various operations. The control unit decodes
instructions and generates the internal control signals that perform the requested
operations. The outputs of the control unit drive the execution unit, which contains the
arithmetic logic unit (ALU), CPU registers, and bus interface.
COP — See "computer operating properly module (COP)."
CPU — See “central processor unit (CPU).”
CPU12 — The CPU of the MC68HC12 Family.
CPU clock — Bus clock select bits BCSP and BCSS in the clock select register (CLKSEL)
determine which clock drives SYSCLK for the main system, including the CPU and buses.
When EXTALi drives the SYSCLK, the CPU or bus clock frequency (fo) is equal to the
EXTALi frequency divided by 2.
CPU cycles — A CPU cycle is one period of the internal bus clock, normally derived by dividing
a crystal oscillator source by two or more so the high and low times will be equal. The
length of time required to execute an instruction is measured in CPU clock cycles.
CPU registers — Memory locations that are wired directly into the CPU logic instead of being
part of the addressable memory map. The CPU always has direct access to the
information in these registers. The CPU registers in an M68HC12 are:
•
A (8-bit accumulator)
•
B (8-bit accumulator)
– D (16-bit accumulator formed by concatenation of
accumulators A and B)
•
IX (16-bit index register)
•
IY (16-bit index register)
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•
SP (16-bit stack pointer)
•
PC (16-bit program counter)
• CCR (8-bit condition code register)
cycle time — The period of the operating frequency: tCYC = 1/fOP.
D — See “accumulators (A and B or D).”
Freescale Semiconductor, Inc...
decimal number system — Base 10 numbering system that uses the digits zero through nine.
duty cycle — A ratio of the amount of time the signal is on versus the time it is off. Duty cycle is
usually represented by a percentage.
ECT — See “enhanced capture timer.”
EEPROM — Electrically erasable, programmable, read-only memory. A nonvolatile type of
memory that can be electrically erased and reprogrammed.
EPROM — Erasable, programmable, read-only memory. A nonvolatile type of memory that can
be erased by exposure to an ultraviolet light source and then reprogrammed.
enhanced capture timer (ECT) — The HC12 Enhanced Capture Timer module has the features
of the HC12 Standard Timer module enhanced by additional features in order to enlarge
the field of applications.
exception — An event such as an interrupt or a reset that stops the sequential execution of the
instructions in the main program.
fetch — To copy data from a memory location into the accumulator.
firmware — Instructions and data programmed into nonvolatile memory.
free-running counter — A device that counts from zero to a predetermined number, then rolls
over to zero and begins counting again.
full-duplex transmission — Communication on a channel in which data can be sent and
received simultaneously.
hexadecimal — Base 16 numbering system that uses the digits 0 through 9 and the letters A
through F.
high byte — The most significant eight bits of a word.
illegal address — An address not within the memory map
illegal opcode — A nonexistent opcode.
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Glossary
index registers (IX and IY) — Two 16-bit registers in the CPU. In the indexed addressing
modes, the CPU uses the contents of IX or IY to determine the effective address of the
operand. IX and IY can also serve as a temporary data storage locations.
input/output (I/O) — Input/output interfaces between a computer system and the external world.
A CPU reads an input to sense the level of an external signal and writes to an output to
change the level on an external signal.
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instructions — Operations that a CPU can perform. Instructions are expressed by programmers
as assembly language mnemonics. A CPU interprets an opcode and its associated
operand(s) and instruction.
inter-IC bus (I2C) — A two-wire, bidirectional serial bus that provides a simple, efficient method
of data exchange between devices.
interrupt — A temporary break in the sequential execution of a program to respond to signals
from peripheral devices by executing a subroutine.
interrupt request — A signal from a peripheral to the CPU intended to cause the CPU to
execute a subroutine.
I/O — See “input/output (I/0).”
jitter — Short-term signal instability.
latch — A circuit that retains the voltage level (logic 1 or logic 0) written to it for as long as power
is applied to the circuit.
latency — The time lag between instruction completion and data movement.
least significant bit (LSB) — The rightmost digit of a binary number.
logic 1 — A voltage level approximately equal to the input power voltage (VDD).
logic 0 — A voltage level approximately equal to the ground voltage (VSS).
low byte — The least significant eight bits of a word.
M68HC12 — A Motorola family of 16-bit MCUs.
mark/space — The logic 1/logic 0 convention used in formatting data in serial communication.
mask — 1. A logic circuit that forces a bit or group of bits to a desired state. 2. A photomask used
in integrated circuit fabrication to transfer an image onto silicon.
MCU — Microcontroller unit. See “microcontroller.”
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memory location — Each M68HC12 memory location holds one byte of data and has a unique
address. To store information in a memory location, the CPU places the address of the
location on the address bus, the data information on the data bus, and asserts the write
signal. To read information from a memory location, the CPU places the address of the
location on the address bus and asserts the read signal. In response to the read signal,
the selected memory location places its data onto the data bus.
memory map — A pictorial representation of all memory locations in a computer system.
Freescale Semiconductor, Inc...
MI-Bus — See "Motorola interconnect bus".
microcontroller — Microcontroller unit (MCU). A complete computer system, including a CPU,
memory, a clock oscillator, and input/output (I/O) on a single integrated circuit.
modulo counter — A counter that can be programmed to count to any number from zero to its
maximum possible modulus.
most significant bit (MSB) — The leftmost digit of a binary number.
Motorola interconnect bus (MI-Bus) — The Motorola Interconnect Bus (MI Bus) is a serial
communications protocol which supports distributed real-time control efficiently and with
a high degree of noise immunity.
Motorola scalable CAN (msCAN) — The Motorola scalable controller area network is a serial
communications protocol that efficiently supports distributed real-time control with a very
high level of data integrity.
msCAN — See "Motorola scalable CAN".
MSI — See "multiple serial interface".
multiple serial interface — A module consisting of multiple independent serial I/O sub-systems,
e.g. two SCI and one SPI.
multiplexer — A device that can select one of a number of inputs and pass the logic level of that
input on to the output.
nibble — A set of four bits (half of a byte).
object code — The output from an assembler or compiler that is itself executable machine code,
or is suitable for processing to produce executable machine code.
opcode — A binary code that instructs the CPU to perform an operation.
open-drain — An output that has no pullup transistor. An external pullup device can be
connected to the power supply to provide the logic 1 output voltage.
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Glossary
operand — Data on which an operation is performed. Usually a statement consists of an
operator and an operand. For example, the operator may be an add instruction, and the
operand may be the quantity to be added.
oscillator — A circuit that produces a constant frequency square wave that is used by the
computer as a timing and sequencing reference.
OTPROM — One-time programmable read-only memory. A nonvolatile type of memory that
cannot be reprogrammed.
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overflow — A quantity that is too large to be contained in one byte or one word.
page zero — The first 256 bytes of memory (addresses $0000–$00FF).
parity — An error-checking scheme that counts the number of logic 1s in each byte transmitted.
In a system that uses odd parity, every byte is expected to have an odd number of logic
1s. In an even parity system, every byte should have an even number of logic 1s. In the
transmitter, a parity generator appends an extra bit to each byte to make the number of
logic 1s odd for odd parity or even for even parity. A parity checker in the receiver counts
the number of logic 1s in each byte. The parity checker generates an error signal if it finds
a byte with an incorrect number of logic 1s.
PC — See “program counter (PC).”
peripheral — A circuit not under direct CPU control.
phase-locked loop (PLL) — A clock generator circuit in which a voltage controlled oscillator
produces an oscillation which is synchronized to a reference signal.
PLL — See "phase-locked loop (PLL)."
pointer — Pointer register. An index register is sometimes called a pointer register because its
contents are used in the calculation of the address of an operand, and therefore points to
the operand.
polarity — The two opposite logic levels, logic 1 and logic 0, which correspond to two different
voltage levels, VDD and VSS.
polling — Periodically reading a status bit to monitor the condition of a peripheral device.
port — A set of wires for communicating with off-chip devices.
prescaler — A circuit that generates an output signal related to the input signal by a fractional
scale factor such as 1/2, 1/8, 1/10 etc.
program — A set of computer instructions that cause a computer to perform a desired operation
or operations.
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program counter (PC) — A 16-bit register in the CPU. The PC register holds the address of the
next instruction or operand that the CPU will use.
pull — An instruction that copies into the accumulator the contents of a stack RAM location. The
stack RAM address is in the stack pointer.
pullup — A transistor in the output of a logic gate that connects the output to the logic 1 voltage
of the power supply.
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pulse-width — The amount of time a signal is on as opposed to being in its off state.
pulse-width modulation (PWM) — Controlled variation (modulation) of the pulse width of a
signal with a constant frequency.
push — An instruction that copies the contents of the accumulator to the stack RAM. The stack
RAM address is in the stack pointer.
PWM period — The time required for one complete cycle of a PWM waveform.
RAM — Random access memory. All RAM locations can be read or written by the CPU. The
contents of a RAM memory location remain valid until the CPU writes a different value or
until power is turned off.
RC circuit — A circuit consisting of capacitors and resistors having a defined time constant.
read — To copy the contents of a memory location to the accumulator.
register — A circuit that stores a group of bits.
reserved memory location — A memory location that is used only in special factory test modes.
Writing to a reserved location has no effect. Reading a reserved location returns an
unpredictable value.
reset — To force a device to a known condition.
SCI — See "serial communication interface module (SCI)."
serial — Pertaining to sequential transmission over a single line.
serial communications interface module (SCI) — A module that supports asynchronous
communication.
serial peripheral interface module (SPI) — A module that supports synchronous
communication.
set — To change a bit from logic 0 to logic 1; opposite of clear.
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shift register — A chain of circuits that can retain the logic levels (logic 1 or logic 0) written to
them and that can shift the logic levels to the right or left through adjacent circuits in the
chain.
signed — A binary number notation that accommodates both positive and negative numbers.
The most significant bit is used to indicate whether the number is positive or negative,
normally logic 0 for positive and logic 1 for negative. The other seven bits indicate the
magnitude of the number.
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software — Instructions and data that control the operation of a microcontroller.
software interrupt (SWI) — An instruction that causes an interrupt and its associated vector
fetch.
SPI — See "serial peripheral interface module (SPI)."
stack — A portion of RAM reserved for storage of CPU register contents and subroutine return
addresses.
stack pointer (SP) — A 16-bit register in the CPU containing the address of the next available
storage location on the stack.
start bit — A bit that signals the beginning of an asynchronous serial transmission.
status bit — A register bit that indicates the condition of a device.
stop bit — A bit that signals the end of an asynchronous serial transmission.
subroutine — A sequence of instructions to be used more than once in the course of a program.
The last instruction in a subroutine is a return from subroutine (RTS) instruction. At each
place in the main program where the subroutine instructions are needed, a jump or branch
to subroutine (JSR or BSR) instruction is used to call the subroutine. The CPU leaves the
flow of the main program to execute the instructions in the subroutine. When the RTS
instruction is executed, the CPU returns to the main program where it left off.
synchronous — Refers to logic circuits and operations that are synchronized by a common
reference signal.
timer — A module used to relate events in a system to a point in time.
toggle — To change the state of an output from a logic 0 to a logic 1 or from a logic 1 to a logic 0.
tracking mode — A mode of PLL operation with narrow loop bandwidth. Also see ‘acquisition
mode.’
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two’s complement — A means of performing binary subtraction using addition techniques. The
most significant bit of a two’s complement number indicates the sign of the number (1
indicates negative). The two’s complement negative of a number is obtained by inverting
each bit in the number and then adding 1 to the result.
unbuffered — Utilizes only one register for data; new data overwrites current data.
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unimplemented memory location — A memory location that is not used. Writing to an
unimplemented location has no effect. Reading an unimplemented location returns an
unpredictable value.
variable — A value that changes during the course of program execution.
VCO — See "voltage-controlled oscillator."
vector — A memory location that contains the address of the beginning of a subroutine written
to service an interrupt or reset.
voltage-controlled oscillator (VCO) — A circuit that produces an oscillating output signal of a
frequency that is controlled by a dc voltage applied to a control input.
waveform — A graphical representation in which the amplitude of a wave is plotted against time.
wired-OR — Connection of circuit outputs so that if any output is high, the connection point is
high.
word — A set of two bytes (16 bits).
write — The transfer of a byte of data from the CPU to a memory location.
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DRM010/D
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