CMLMICRO DE8661

CML Microcircuits
COMMUNICATION SEMICONDUCTORS
DE8661
V.22bis User Manual
for a "socket modem"
UM8661/4 June 2004
1.0
Provisional Issue
Features
• CMX866-based socket modem Reference Design
• FCC68 or CTR21 DAA
• Fully Isolated 2-Wire Line Interface
• Single 3V or 5V dc power supply
operation
• Opto Isolated Ring Detect Circuitry and
OptoMOS Hook Relay
• Break-off PCB sections support
'desktop' and 'socket' modem use
• Integral AT Command Set with 'Fast Connect'
• PCB layout data provided
• PC Controlled via Terminal Emulator
1.1
Brief Description
The DE8661 Demonstration Board is a reference design for the CMX866 V.22 bis AT command modem
IC. The main "socket modem" section contains the CMX866 and associated components in addition to
the line interface components. Attached to the main section are two break-off sections which contain a 9pin D type socket for PC serial communications, RJ11 line connector, supply voltage connector and a
hook-state LED. The CMX866 contains an on-chip µController, which interprets AT Commands issued via
a standard terminal emulator program running on a host PC or via an external µController.
Interfacing to the Demonstration Board can be via socket pins on the socket modem section, or via the
connectors provided on the break-off sections. The board can be operated at 3V or 5V dc, which must be
provided by an external, regulated power supply.
The PCB has been laid out for both CTR21 and FCC68 compliant DAA designs. However the
components fitted are for the simplified European/FCC68 design. Users wishing to convert to CTR21
should contact CML.
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CONTENTS
Page
Section
1.0
Features ............................................................................................... 1
1.1
Brief Description ................................................................................. 1
1.2
Preliminary Information ...................................................................... 4
1.2.1 Equipment............................................................................... 4
1.2.2 Handling Precautions ............................................................. 4
1.2.3 Approvals ................................................................................ 4
1.3
Quick Start........................................................................................... 5
1.3.1 Setting-Up ............................................................................... 5
1.3.2 Operation ................................................................................ 5
1.4
Signal Lists.......................................................................................... 7
1.5
Circuit Schematics and Board Layout ............................................... 9
1.6
Detailed Description.......................................................................... 11
1.6.1 Hardware Description ........................................................... 11
1.6.2 Serial Interface ...................................................................... 12
1.6.3 Reset Function...................................................................... 13
1.6.4 AT Command and S-Register Summary.............................. 15
1.6.5 General Description of AT Commands................................ 17
1.6.6 Modem Result Codes ........................................................... 18
1.6.7 Terminal Emulator ................................................................ 18
1.7
Performance Specification ............................................................... 20
1.7.1 Electrical Performance ......................................................... 20
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DE8661
Modem
or
Telephone Line
Simulator
J3
J61
DE8661
Power
Supply
J26/J41
J4
RS232 Cable
IBM-PC
Figure 1 System Diagram
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1.2
Preliminary Information
1.2.1
Equipment
DE8661
The following equipment is needed to use this demonstration board:
1.2.1.1 3Vdc or 5Vdc Regulated Power Supply
1.2.1.2 A PC equipped with a serial port running a terminal emulation program such as Microsoft's
HyperTerminal.
1.2.2
Handling Precautions
1.2.2.1 Static Protection
This product uses low power CMOS circuits, which can be damaged by electrostatic discharge.
Partially damaged circuits can function erroneously, leading to misleading results. Observe ESD
precautions at all times when handling this product.
1.2.2.2 Contents - Unpacking
Please ensure that you have received all of the items on the separate information sheet
(EK8661) and notify CML within 7 working days if the delivery is incomplete.
1.2.3
Approvals
This product is designed to meet CTR21 or FCC68 telecom approval requirements. Users
are advised to observe local statutory requirements which may apply to this product,
before direct or indirect connection to any public telecommunication system.
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1.3
DE8661
Quick Start
This section provides instructions for users who wish to experiment immediately with the
demonstration board. A fuller description of the board and its use appears later in this document.
1.3.1
Setting-Up
THE DE8661 COMES PRE-CONFIGURED AS AN FCC68 MODEM, USING THE CMX866 D6
28-pin SSOP DEVICE, FOR OPERATION AT 5.0 VOLTS. See section 1.6 for the alternative
component values required for 3.0V or CTR21 operation.
An RJ11 (US style) phone jack socket, J3, for 2-wire line connection is provided on one of the
break-off board sections. Power can be connected via socket pins 61(VDD) and 41(GND) (see
figure 2.0, section 1.5), or via jumper JP4 on the break-off section.
Attach the 9-way RS232 cable between connector J4 and the serial port of the PC. Connect an
external modem/line simulator to the evaluation kit using a suitable RJ11 telephone cable (not
supplied).
The DE8661 is supplied with the break-off sections of the board intact. If a socket modem using
the industry standard footprint is required, detach these break-off sections from the
Demonstration Board PCB by using a suitable tool to scribe along the perforations that join the
break-off sections to the main PCB. Scribe on both top and bottom sides of the board and ensure
that the scribed line completely cuts any copper tracks entering or leaving the break-off sections
from the main PCB. When this is done, gently break-off the first section on which connector J4
(9-pin D Type socket) is mounted, then break-off the second section on which the RJ11 socket is
mounted. All connections to the remaining socket modem must now be made through the PCB
connector pins.
1.3.2
Operation
The DE8661 demonstration board allows the user to perform calling, answering and simple data
transfer with an external third party modem (not supplied). In order to provide central
office/exchange dc line voltage, a suitable central office simulator is also required.
The board is controlled by the AT command set described in Section 1.6.4. These commands
can be sent to the DE8661 from a terminal emulator program running on a host PC or from an
external µController. A suitable emulator is the ‘HyperTerminal’ program, which operates under
Windows 95 upwards. The DE8661 AT command set consists of Basic, Extended and CML
Specific commands.
The board has two modes of operation:
AT Command Mode
In this mode the CMX866 on-chip AT command processor checks to see if the user has typed a
valid AT command. When a valid command is received, it is interpreted then actioned by the
CMX866. When operating in this mode, the user can instruct the DE8661 to manually answer a
call, originate a call, go on/off hook, read/write to S-registers, issue CML specific AT commands,
and perform any number of other AT command functions. The board always starts in AT
Command mode after power is applied and board initialisation is complete.
The Dial and Answer commands will execute the relevant DTMF transmit, call progress tone
detection and negotiation (handshaking) functions before a connection to a remote
modem/simulator can be established. Negotiation may be aborted by pushing any key.
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Note: If the S0 register is modified to a non-zero value during this operating mode the CMX866
will poll its status register every 20ms to check for ring detection. If valid ringing is detected the
DE8661 will automatically answer a call after n ring cycles, where n is equivalent to the contents
of the S0 register.
Data Transfer Mode
After gaining a connection (i.e. successful negotiation) with a remote modem the board will
operate in data transfer mode. In this mode the board will transmit all the data it receives from
the RS232 computer terminal or external µController to the remote modem via the 2-wire line.
Likewise any data received from the remote modem via the 2-wire line will be sent to the RS232
computer terminal or external µController.
Whilst operating in this mode the data stream from the RS232 computer terminal or external
µController is monitored for the escape code sequence (+++). If this sequence is encountered
during data transfer the board will revert to on-line AT command mode. Whilst in on-line AT
command mode, the remote modem connection may be aborted by typing ATH0 (instructs the
DE8661 to go on-hook). Alternatively the user can enter relevant AT commands or return to data
transfer mode by using the ATO command.
The modem line speed is much lower than the speed of the RS232 interface (RS232 is running at
9600bps). To prevent the CMX866 internal data buffer from overflowing, the data flow between
the host system and the RS232 interface on the DE8661 is controlled using the CTS (Clear to
Send) hardware handshake line.
The CMX866 settings used during negotiation and data transfer will be based on the contents of
the S-registers when the call was originated or answered. The S-registers are described in
Section 1.6.4. Certain S-register settings (relevant to the CMX866 configuration), modified
during on-line AT command mode, will only take effect when a new call is originated or
answered. For example, new CMX866 Tx gain settings (S25 register) modified in on-line AT
command mode will be ignored until the next call.
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1.4
DE8661
Signal Lists
CONNECTOR PINOUT
Connector
Ref.
Signal
Name
Signal
Type
Description
J1
TIP
Bi
Socket pin - Tip
J2
RING
Bi
Socket pin – Ring
3
RING
Bi
RJ11 connector – Ring
4
TIP
Bi
RJ11 connector – Tip
1
DCD
Output
9-pin D Type connector – Host DCD
2
RXD
Output
9-pin D Type connector – Host RXD
3
TXD
Input
9-pin D Type connector – Host TXD
4
DTR
Input
9-pin D Type connector – Host DTR
5
VSS
Power
9-pin D Type connector – Host GND
6
DSR
Output
9-pin D Type connector - Host DSR
7
RTS
Input
9-pin D Type connector – Host RTS
8
CTS
Output
9-pin D Type connector - Host CTS
9
RI
Output
9-pin D Type connector – Host RI
J24
/RESET
Input
Socket pin – CMX866 reset
J26
VSS
Power
VSS connection
J29
N/C
J30
N/C
J31
N/C
J32
N/C
J33
/RTSTTL
Input
Socket pin – CMX866 RTSN
J34
/RXDTTL
Output
Socket pin – CMX866 RXD
J35
/TXDTTL
Input
Socket pin – CMX866 TXD
J36
/RITTL
Output
Socket pin – CMX866 RIN
J37
/DSRTTL
Output
Socket pin – CMX866 DSRN
J38
/CTSTTL
Output
Socket pin – CMX866 CTSN
J39
/DCDTTL
Output
Socket pin – CMX866 DCDN
J40
/DTRTTL
Input
Socket pin – CMX866 DTRN
J41
Vss
Power
Vss connection
J61
VDD
Power
+ve power from external power supply
J62
N/C
J63
N/C
J3
J4
Connector
Pin No.
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LEDs
LED
Ref.
Description
D7
Illuminated when the line is in an off-hook state
JUMPERS
Jumper
Ref.
Positions
Default
Position
Description
JP1
1-2
S/C
RS232 Receiver enable (U8)
JP4
1-2
O/C
Allows a supply voltage to be physically connected to the
top side of the PCB.
Notes: Bi
S/C
O/C
N/C
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=
=
=
Bidirectional
Short Circuit
Open Circuit
Not Connected
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1.5
DE8661
Circuit Schematics and Board Layout
For clarity circuit schematics are available as separate, high resolution, files.
TIP J1
RING J2
J63 N/C
J62 N/C
J61 VDD
J41 GND
J40 /DTRTTL
J39 /DCDTTL
J38 /CTSTTL
J37 /DSRTTL
J36 /RITTL
J35 /TXDTTL
J34 /RXDTTL
J33 /RTSTTL
/RESET J24
GND J26
N/C J29
N/C J30
N/C J31
N/C J32
Figure 2 Socket Section Pinout (topview)
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Figure 3a DE8661 Top Silk Screen
Figure 3b DE8661 Bottom Silk Screen
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1.6
Detailed Description
1.6.1
Hardware Description
DE8661
1.6.1.1 Operating Voltage
The DE8661 can be operated at a VDD of 3 or 5Vdc (default), supplied by an external regulated
power supply. Tables of component values for CTR21 and FCC68 DAAs are shown below:
CTR21 DAA
VDD
3.0 V
5.0 V
R6
91K (93.5k)
56K (57.6k)
R7
160k
180k
C24
180pF
220pF
FCC68 DAA
VDD
R6
R7
C24
3.0 V
100K (107k)
160k
39pF
5.0 V
62K (64.9k)
180k
47pF
(The values shown in brackets are optimal values)
R12
220R
620R
D1
3.0V
4.3V
R12
220R
620R
D1
3.0V
4.3V
1.6.1.2 Clock/Oscillator
The CMX866 is clocked at a frequency of 11.0592MHz, which is provided by crystal X1.
1.6.1.3 On-hook Caller ID
This function provides a high impedance, on-hook AC path for the routing of Caller ID signals to
the CMX868. Components C9, R5 provide this transmission path. C9 bypasses the optoMOS
relay hook switch, allowing AC signals to pass through T1 when the socket modem is in an onhook state. The CMX866 has a switched inverting input (pin 11) which is used to compensate for
input signal losses incurred while in the on-hook state.
1.6.1.4 Simplified FCC68 Compliant DAA, as Shipped
The values of R4, R6, R7, R8, R9, C8 and C24 are optimal values with respect to the Midcom
82111 wet line transformer. Parts C10 and D4 are not required for this simplified design but are
replaced with 0Ω links.
1.6.1.5 CTR21 Compliant DAA
Components R10, R11, C11, D4, D5, U4 and U5 may be fitted to provide a 60mA current limit
required by CTR21. An alternative wet line transformer, the Midcom 82107, must be fitted. Parts
C10, C24, and R6 also have different values, to match the characteristics of the 82107
transformer and the CTR21 reference impedance.
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1.6.1.6 Line Protection
Line protection is provided by the Sidactor component E1. Sidactor is the trade name for a type
of Transient Voltage Suppressor (TVS) manufactured by Teccor Electronics.
1.6.1.7 Ring Detection
The ring detect threshold is approximately 20VRMS.
1.6.2
Serial Interface
The DE8661 can be controlled by sending AT commands over a direct serial interface from an
external µController, or with a standard terminal emulator program running on a host PC, and
connected via RS-232. This latter option makes use of the 9-pin D type socket and MAX3237
RS-232 Transceiver chip, both of which are fitted to one of the break-off sections of the DE8661
PCB. Asynchronous communication is used with 9600 baud, 8-bit words, no parity and 1 stop-bit.
The 9600 baud rate necessitates CTS flow control to moderate the data rate. The CTS flow
control method provided on the CMX866 will also work with the RTS/CTS handshake protocol
used by some µControllers.
If using an external µController to control the DE8661, its Request To Send signal should be
taken low, which takes the CMX866 RTSN pin low. Data is asserted (AT commands or data), by
the external µController onto the CMX866 TXD pin. When the DE8661 is ready to accept this
data from the external host µController the CMX866 will takes its CTSN pin low. The data should
be sent as 8-bit bytes, encapsulated by a start bit (low) and a stop bit (high). The DE8661 should
be presented with continuous mark (stop bits) when the external µController has no data to send.
As each byte is received it is stored in an on-chip, 48-byte AT command buffer when in
Command mode or in an on-chip, 16-byte receive data buffer when in Data Transfer mode. The
CMX866 will take its CTSN pin high when either buffer is full and will ignore further information
on the TXD pin until the on-chip µController is ready to accept it. At this time, the CMX866 will
once again take its CTSN pin low to signify its readiness to accept more data, providing the
RTSN pin is already low. If the external µController does not have a Request To Send signal, the
RTSN pin should be permanently wired low. When RTSN is inactive high, CTSN follows RTSN
and becomes inactive high, thus there is no data flow in either direction between the DE8661 and
the external µController. As the incoming AT command is being interpreted, any phone number is
identified and stored separately in the 24-byte on-chip phone number buffer.
When the DE8661 is in Data Transfer mode and a signal is received from the phone line
exceeding the minimum amplitude threshold, the CMX866 will attempt to demodulate the signal
and assert the received data on its RXD pin, after a complete byte has been demodulated. At the
same time it will take its DCDN pin low. There is a 24-byte message buffer in the CMX866
receive path but, as the received data always arrives at slower than 9600 baud, there is no need
for a flow control handshake in the receive path. It is assumed that the external µController will
absorb all of the data presented to it without the need for flow control and will ignore continuous
mark (stop bits) when there is no received data. If the received signal is below the detection
threshold or the DE8661 is not in Data Transfer mode, the CMX866 will take its DCDN and RXD
pins high.
If the CMX866 receives a RING signal on the RD and RT pins, such that the detection threshold
is exceeded, then this condition will be signalled to the external µController by the CMX866
taking its RIN pin low. This pin follows the output of the ring detector, so will go low for each burst
of RING signal. If the CMX866 is in a Powersave or 'Zero-Power' state, it will be woken up and
the DSRN pin will go low once the on-chip µController is ready to receive communications
through the serial port. This wake up process takes about 30ms from 'Zero-Power' state, as the
VBIAS pin has to charge the external reservoir capacitor and the crystal oscillator has to start up
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and stabilise before the CMX866 can initialise itself. From the Powersave state this wake up
process takes about 10µs, as the oscillator and the VBIAS pin are already stable.
The CMX866 DSRN and DTRN pins do not act as a handshake with the external µController. The
DSRN pin indicates the operational status of the on-chip µController (low = ready to
communicate with an external µController). The DTRN pin is used for taking the CMX866 out of
Powersave or 'Zero-Power' state. It effectively acts as a device wake up, in the same manner as
the RING signal, and becomes active on the high to low transition. A high to low transition on the
DTRN pin is ignored if the device is already 'woken up'. If the external µController does not have
a DTR signal, the DTRN pin should be permanently wired to the TXD pin. When the CMX866 is
in a Powersave or 'Zero-Power' state, the RXD, CTSN, DSRN, DCDN and RIN pins will be
permanently high. The condition of the TXD, RTSN and DTRN pins is not important.
Depending on the &Dn configuration, if the DTRN pin on the CMX866 is taken high at any time
whilst the DE8661 is in Data Transfer mode, a fixed, 100ms timeout is started. On completion of
the timeout, the DE8661 will return to AT Command mode, enabling further AT commands to be
sent. If the DTRN pin goes high whilst the DE8661 is in AT Command mode, the action is
ignored. AT commands can be sent providing CTSN and RTSN are low (ie DTRN can be either
high or low). A low to high transition on the ESC pin also has the same effect of returning the
DE8661 from Data Transfer mode to Command mode, but with immediate effect. The &Dn
command configures these options, see section 1.5.4.4 for more details.
If the RTSN pin of the CMX866 is taken high at any time whilst the DE8661 is in Data Transfer
mode, a timeout is started whose value is set in the S28 register (0 = timeout disabled). On
completion of the timeout, the DE8661 will return to AT Command mode and take CTSN high. If
the RTSN pin goes high whilst the DE8661 is in AT Command mode, the CTSN pin goes high
and the action on the RTSN pin is ignored. Information transfer can only restart when the RTSN
pin is taken low again and the CMX866 responds by taking CTSN low.
1.6.3
Reset Function
The CMX866 as fitted to the DE8661 has an internal power-up reset function which is activated
whenever power is applied to the board. This reset function resets all of the on-chip µController
registers, including the S-Register settings, and then performs an initialisation sequence which
resets the internal DSP and subsequently places it in a powersave state, loads the factory default
values into the S-Registers and places the on-chip µController into an operating state. This
internal power-up reset function is OR-ed with the RESETN pin.
When the RESETN pin is taken low, i.e. SW1 on the break-off section is activated or a low signal
is applied to pin 24 of the DE8661 the reset operation described above is performed.
When the CMX866 first enters the operating state, it reports its configuration as follows:
•
CMX866 waits for DTRN to go active (low) - to wake up the device
•
CMX866 takes the DSRN pin active (low) to indicate its readiness to
communicate with an external µController
•
CMX866 waits for RTSN to go active (low)
•
CMX866 sends "CMX866" identification message to external µController
(equivalent to the external µController issuing an ATI0 command)
•
The on-chip µController now powers up the DSP part of the CMX866
•
The DSP is automatically reset then requested to perform an internal diagnostic self-check,
which takes about 2.9ms to complete
•
On successful completion, CMX866 sends "DSP checksum OK" identification message to
the external µController. If not successful, CMX866 sends "DSP Error" message to the
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external µController. In the latter case, the CMX866 should be reset again by taking the
RESETN pin low
•
The on-chip µController now powers down the DSP part of the CMX866
•
The on-chip µController is now in the Command mode operating state and is ready to
accept AT commands from the serial interface, approximately 55ms after DTRN goes low
•
CMX866 takes the CTSN pin active (low) to indicate its readiness to
communicate with an external µController
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1.6.4
DE8661
AT Command and S-Register Summary
AT Command
Parameters
Function
A
Answer Command - Answer and establish a connection when off-hook
A/
Re-execute last command
Select Communications Standard
(Mapped to S27)
Bn
Dn ... n
or DTn ... n
n = 0 V.22bis 2400bps QAM
n = 1 V.22 1200bps DPSK
n = 2 V.23 Tx 75bps, Rx 1200bps (Master)
n = 0..9
n = 3 V.23 Tx 1200bps, Rx 75bps(Slave)
n = 4 Reserved
n = 5 V.21 300bps FSK
n = 6 Bell 212A 1200bps DPSK
n = 7 Bell 202 Tx 150bps Rx 1200bps
n = 8 Bell 202 Tx 1200bps Rx 150bps
n = 9 Bell 103 300bps FSK
n = 0..9, A..D, *,# Dial Command - DTMF dials the subsequent Directory Number
,
Dial Command Modifier - Delay during dialling - time in S8 register
!
Dial Command Modifier- Send a line break - time in S29 register
;
Dial Command Modifier - command mode after dialling, no handshake
DL
Default
n=0
Dial Command - Redial last number
En
n = 0,1
Command echo, 0=off, 1=on
n=1
Hn
n = 0,1
Switch Hook Control, 0=on-hook, 1=off-hook
n=0
In
n=0
Nn
n = 0,1
O
Qn
Identification - Returns the modem's product identification
V.22bis Fallback to V.22 option, 0=none, 1=automatic
Go online in Data mode (from Command mode)
n = 0,1
RO
Enable(n=0)/Disable(n=1) return of modem result codes
Execute V.23 or Bell 202 turnaround if enabled (see S14 and S24)
then go online in Data mode
Function
AT Command
Parameters
Sn?
n = 0..29
S-Register "n" Read - Display specified S Register contents
Sn=x
Vn
Xn
n = 0..29
n =0,1
n = 0..3
S-Register "n" Write - Write to specified S Register
Return result codes as numbers (n=0) or words (n=1)
Calling and Response Characteristics
Z
&Cn
n=1
n=0
Default
n=0
n=3
Restore factory profile for CMX866
n = 0,1
&Dn
n= 0..2
&Gn
&Tn
n = 0..2
n = 0,3..6
DCD always on (n=0) or DCD follows carrier (n=1)
n=1
DTR signal procedure
n=2
Guard Tone Select - Disable (n=0), Enable 550Hz (n=1) or 1800Hz (n=2)
User accessible Loopback Tests and Diagnostics
n=0
n=0
Returns current configuration
&V
'Zero-Power' state (n=0) or Powersave state (n=1)
&Zn
n = 0,1
@Rn?
n = 00..FF
DSP Register "n" Read - Display specified DSP Register contents
@Rn=x
n = 00..FF
DSP Register "n" Write - Write to specified DSP Register
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S Registers
DE8661
Parameters
Function
S0
0…255
Number of rings before answering, 0 = Auto-answer disabled
S1
0…255
Number of rings received
Default
2
0
S2
0-127
Escape character value
S3
0-127
Carriage return character value
+
S4
0-127
Line feed character value
LF
S5
0-127
Backspace character value
BS
S6
2…255
Waiting time in seconds for dial tone or before blind dialling
4s
S7
2…255
Maximum waiting time in seconds for carrier
50s
S8
0...255
Pause time in seconds for "," dial modifier
2s
S9
1...255
Reserved
CR
S10
1…255
Lost carrier to hang up delay in units of 100ms
700ms
S11
5…255
DTMF tone duration and interdigit pause duration in units of 10ms
100ms
S12
0…255
Escape code guard time in units of 50ms
0…255
General Options: bypass Answer Tone Detect sequence for 'Fast Connect'
S13
S14
1s
Reserved
$92
S15
0…255
Loopback carrier off time in milliseconds
80ms
S16
0…255
Drop time for loopback in milliseconds
60ms
S17
0…255
Handshake timeout (Answering) in seconds
30s
S18
0…255
Loopback timer (0= no timeout) in seconds
0s
S19
Reserved for test functions
S20
Reserved
S21
0…255
Loopback and Power states
$10
S22
0…255
Calling and response characteristics selection
$C0
S Registers
Parameters
S23
0…255
Guard tone selection
S24
0…255
Equaliser, DCD, DTR status and modulation fallback
$A9
S25
0…255
Tx Gain, Tx data format
$B0
S26
0…255
Rx Gain, Rx data format, overspeed (2.3% default) setting
$30
S27
0…255
Communications Protocol
$00
S28
0…255
RTSN Timeout for return to Command mode from Data mode in seconds
0s
S29
0…255
Timed Break Recall period in centiseconds
Xn Register
Parameter
n
0
Function
Default
$00
300ms
Calling and Response Characteristics
(Mapped to S22 register)
1
Ignore dial tones and busy tones, return CONNECTxxxx or NO CARRIER
Ignore busy tone, wait for dial tone to dial. Return NO DIAL TONE or
CONNECT xxxx or NO CARRIER
2
Ignore dial tone. If busy tone detected, return BUSY. Return CONNECT xxxx
3
Return NO DIAL TONE, BUSY, CONNECT xxxx, or NO CARRIER
 2004 CML Microsystems Plc
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DE8661 Reference Design and Demonstration Board
&Dn Register
Parameter
DTR action
n
(Mapped to S24 register)
0
&Gn Register
Ignore DTR signal
1
Go to command state when on to off transition occurs
2
Hang up and go to command state when on to off transition occurs
Parameter
Guard Tone action
n
&Tn Register
1.6.5
DE8661
(Mapped to S23 register)
0
Disabled
1
Enabled 550Hz
2
Enabled 1800Hz
Parameter
Test function
n
0
(Mapped to S21 register)
Terminate test
1
Reserved
2
Reserved
3
Local digital loopback
4
Enable remote request for digital loopback
5
Disable remote request for digital loopback
6
Request remote digital loopback & initiate
General Description of AT Commands
Supported AT commands are listed in section 1.6.4. Valid commands will generate an 'OK' result code
(see section 1.6.6) and invalid commands will be rejected with an 'ERROR' result code, when command
echoing and word result codes are enabled. The CMX866 will send a <LF> character directly after a
<CR> character to ensure compatibility with external µControllers. Any commands which are not fully
implemented will return the result code ‘NYI’ (Not Yet Implemented). AT commands should not be sent to
the on-chip µController until the previous result code (if enabled) has been received.
Each command line (except for A/ and the escape sequence) must begin with the AT prefix and be
terminated with a carriage return <CR>. The CMX866 waits to receive a complete AT command line
before processing it. Embedded spaces are ignored and the case (upper or lower) of characters including
the ‘AT’ does not matter. The command line must not exceed 48 characters (excluding the ‘AT’
characters). The CMX866 will ignore the command line and return an 'ERROR' result code if the line is
not terminated correctly.
All characters in the AT command, including the ‘AT’ and <CR> terminator are echoed (if E1 is set) by
the DE8661 in the order in which they are sent by the external µController.
If when entering an AT command, no command or register name suffix is supplied, a suffix of zero is
assumed. If when changing a register value, no value is supplied a value of zero or an empty string is
assumed, i.e. ATS0=<CR> is equivalent to ATS0=0<CR>.
 2004 CML Microsystems Plc
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DE8661 Reference Design and Demonstration Board
DE8661
Receipt of a back space will cause the DE8661 to send a "backspace, space, backspace" sequence of
characters to the external µController, to allow any terminal which may be connected to the latter to clear
its screen of the last character. Also the last character received will be discarded unless the last
characters received were ‘AT’, ie the ‘AT’ is never deleted.
The escape sequence ‘+++’ (with Guard Time = 1s [see S12 register] before and after the sequence) will
cause the DE8661 to enter AT Command mode from Data Transfer mode and to return an ‘OK’
response.
A detailed description of AT commands and S-Registers can be found in the CMX866 Data Sheet,
available from the CML website.
1.6.6
Modem Result Codes
Numeric Response (Decimal)
00
01
02
03
04
05
06
07
08
09
10
11
12
13
14
15
1.6.7
Alpha Response
OK
CONNECT
RING
NO CARRIER
ERROR
NO DIAL TONE
BUSY
CONNECT 2400
CONNECT 1200
DUAL TONE DETECT
CONNECT 300
CONNECT 1200/75
CONNECT 75/1200
CONNECT 1200/150
CONNECT 150/1200
NYI
(Not Yet Implemented)
Terminal Emulator
If using a terminal emulator to control the DE8661, ‘HyperTerminal’, which is supplied with the
Windows 95/NT installations, is suitable for this purpose.
HyperTerminal Setup
Emulation VT100
ASCII Character set
ASCII Receiving:
COM Port Settings:
Wrap lines that exceed terminal width.
Bits per second
Data bits
Parity
Stop bits
Flow Control
9600
8
None
1
Hardware
Some terminal emulators have been found not to support full hardware flow control when
transferring text files. This could result in data loss when using this facility. If this problem is
experienced users should try using a different terminal emulator.
 2004 CML Microsystems Plc
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DE8661 Reference Design and Demonstration Board
DE8661
To ensure successful negotiation and data transfer between the DE8661 and third party modems,
users should ensure their third party modem is configured to the correct protocol (see third party
AT command documentation).
Note, any sudden loss of the 2-wire line during data transfer will result in loss of carrier and
therefore the demonstration board will hang up and display the NO CARRIER message.
However, due to the lost carrier to hang up delay (S10), a short burst of corrupt characters (noise
generated) will be observed on the HyperTerminal window before the NO CARRIER message is
displayed. These corrupt characters can sometimes match control characters and therefore
modify HyperTerminal’s behaviour. The user is advised to restart HyperTerminal if this happens.
 2004 CML Microsystems Plc
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DE8661 Reference Design and Demonstration Board
1.7
Performance Specification
1.7.1
Electrical Performance
DE8661
1.7.1.1 Absolute Maximum Ratings
Exceeding these maximum ratings can result in damage to the DE8661.
Min.
-0.3
-0.3
-20
Supply (VDD – VSS)
Voltage on any connector pin to VSS
Current into or out of any socket modem connector pin
other than VDD, VSS, TIP and RING
Max.
7.0
VDD + 0.3
+20
Units
V
V
mA
Max.
5.5
Units
V
1.7.1.2 Operating Limits
Correct operation of the DE8661 outside these limits is not implied.
Notes
Supply (VDD – VSS)
Min.
2.7
1.7.1.3 Operating Characteristics
For the following conditions unless otherwise specified:
Evaluation Device Xtal Frequency = 11.0592MHz ±0.01% (100ppm)
VDD = 3.0V or 5.0V, Tamb = +25°C.
Notes
DC Parameters
IDD (socket modem alone - idle)
IDD (demonstration board - idle)
Notes: 1.
 2004 CML Microsystems Plc
1
Min.
Typ.
10
18
Max.
Units
mA
mA
Hook LED off
20
UM8661/4
DE8661 Reference Design and Demonstration Board
DE8661
CML does not assume any responsibility for the use of any circuitry described. No IPR or circuit patent licences are implied.
CML reserves the right at any time without notice to change the said circuitry and any part of this product specification. Evaluation
kits and demonstration boards are supplied for the sole purpose of demonstrating the operation of CML products and are supplied
without warranty. They are intended for use in a laboratory environment only and are not for re-sale, end-use or incorporation into
other equipments. Operation of these kits and boards outside a laboratory environment is not permitted within the European
Community. All software/firmware is supplied "as is" and is without warranty. It forms part of the product supplied and is licensed
for use only with this product, for the purpose of demonstrating the operation of CML products. Whilst all reasonable efforts are
made to ensure that software/firmware contained in this product is virus free, CML accepts no resonsibility whatsoever for any
contamination which results from using this product and the onus for checking that the software/firmware is virus free is placed on
the purchaser of this evaluation kit or development board.
www.cmlmicro.com
For FAQs see: www.cmlmicro.com/products/faqs/
For a full data sheet listing see: www.cmlmicro.com/products/datasheets/download.htm
For detailed application notes: www.cmlmicro.com/products/applications/
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