CMX866
V.22 bis Modem
with AT Commands
D/866/1 December 2001
Advance Information
Features
•
V.22 bis, V.22 and Bell 212A QAM/DPSK
•
V.23, Bell 202, V.21 and Bell 103 FSK
•
Integral AT Command Set with 'Fast Connect'
•
V.23 and Bell 202 'Fast Turnaround'
•
Support for Type 1 Caller Line Identification
•
DTMF/Programmable Tones: Transmit and Receive
•
'Zero-Power' and Powersave Standby Modes
•
Low Power Operation
Applications
•
Telephone Telemetry Systems
•
Remote Utility Meter Reading
•
Security Systems
•
Industrial Control Systems
•
Electronic Cash Terminals / ATMs
•
Pay-Phones
•
Cable TV Set-Top Boxes
•
EPOS Terminals
1.1
Brief Description
The CMX866 is a multi-standard modem for use in telephone based information and telemetry systems.
Control of the device is via AT commands over a simple 9600b/s serial interface, compatible with most
types of host µController. An RS232 compatible interface can be created by the addition of a Level
Converter. The data transmitted and received by the modem is also transferred over the same serial
interface. The on-chip µController interprets these AT commands and controls an internal DSP, which
provides the modem and anciliary functions such as Ring Detection, Call Progress Detection, Hook
Switch control and DTMF autodialling. User-specific DSP functions are also available via the AT
command set.
Hardware support is provided for V.23 and Bell 202 Fast Turnaround and for rapid return to AT Command
mode. A Fast Connect mode has been implemented to reduce modem connection time. Flexible line
driver and receive hybrid circuits are integrated on chip, requiring only passive external components to
build a 2 or 4-wire line interface. Complete examples of 2-wire line interfaces to an external host µC and
to an RS232 interface, including the additional components required for Type 1 CLI, are provided.
The device features a Hook Switch relay drive output and a Ring Detector circuit that remain operational
when the CMX866 is in 'Zero-Power' or Powersave mode, providing an interrupt which can be used to
wake up an external host µC, as well as the CMX866, when line voltage reversal or ringing is detected.
The CMX866 takes 5mA (typ.) from a single 2.7–5.5V supply and comes in 28-pin SSOP/SOIC
packages.
©
2001 Consumer Microcircuits Limited
V.22 bis Modem with AT Commands
CMX866
CONTENTS
Section
1.1
1.2
1.3
1.4
Page
Brief Description..................................................................................1
Block Diagram .....................................................................................3
Signal List ............................................................................................4
External Components..........................................................................6
1.4.1 Ring Detector Interface ...........................................................8
1.4.2 Line Interface...........................................................................9
1.4.3 Serial Interface ...................................................................... 11
1.4.4 RESETN pin........................................................................... 12
General Description........................................................................... 13
1.5.1 Internal Structure .................................................................. 13
1.5.2 Operating States and Data Flow........................................... 14
1.5.3 Functional Description ......................................................... 16
1.5.4 AT Command and Register Set ............................................ 17
1.5.4.1 AT Command and S-Register Summary.................. 17
1.5.4.2 General Description of AT Commands.................... 19
1.5.4.3 AT Commands in Detail............................................ 20
1.5.4.4 Extended AT Commands ......................................... 23
1.5.4.5 S-Registers................................................................ 25
1.5.4.6 Result Codes............................................................. 29
1.5.5 Tx USART .............................................................................. 29
1.5.6 FSK and QAM/DPSK Modulators ......................................... 31
1.5.7 Tx Filter and Equaliser.......................................................... 32
1.5.8 DTMF/Tone Generator .......................................................... 32
1.5.9 Tx Level Control and Output Buffer..................................... 32
1.5.10 Rx DTMF/Tones Detectors.................................................... 33
1.5.11 Rx Modem Filterering and Demodulation............................ 34
1.5.12 Rx Modem Pattern Detectors and Descrambler .................. 35
1.5.13 Rx Data Register and USART ............................................... 35
Application Notes .............................................................................. 37
1.6.1 Hardware Interface ................................................................ 37
1.6.2 Calling Modem AT Commands............................................. 41
1.6.3 Answering Modem AT Commands....................................... 41
1.6.4 RS232 Transaction Sequence .............................................. 42
Performance Specification................................................................ 43
1.7.1 Electrical Performance.......................................................... 43
1.7.1.1 Absolute Maximum Ratings ..................................... 43
1.7.1.2 Operating Limits ....................................................... 43
1.7.1.3 Operating Characteristics ........................................ 44
1.7.2 Packaging.............................................................................. 50
1.5
1.6
1.7
©
2001 Consumer Microcircuits Limited
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V.22 bis Modem with AT Commands
CMX866
1.2
Block Diagram
Figure 1 Block Diagram
©
2001 Consumer Microcircuits Limited
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CMX866
1.3
Signal List
CMX866
D1/D6
Pin No.
1
2
3
4
5
Signal
Name
XTALN
XTAL/CLOCK
N/C
N/C
RDRVN
Type
O/P
I/P
~
~
O/P
The output of the on-chip Xtal oscillator inverter.
The input to the oscillator inverter from the Xtal
circuit or external clock source.
Reserved for future use. Connect this pin to
DV
SS
.
Reserved for future use. Connect this pin to
DV
SS
.
Relay drive output, low resistance pull down to
DV
SS
when active and medium resistance pull
up to DV
DD
when inactive.
The negative supply rail for the digital on-chip
blocks.
Schmitt trigger input to the Ring signal detector.
Connect to DV
SS
if Ring Detector not used.
Open drain output and Schmitt trigger input
forming part of the Ring signal detector.
Connect to DV
DD
if Ring Detector not used.
Schmitt trigger input to an active-low reset pin.
Connect to DV
DD
if no external reset signal
used
The output of the Rx Input Amplifier.
An alternative, switched inverting input to the
Rx Input Amplifier, used to increase the
amplifier gain for the detection of on-hook
signals. If this input is not required, leave the
pin disconnected.
The inverting input to the Rx Input Amplifier
The non-inverting input to the Rx Input
Amplifier. If this pin is to be connected to V
BIAS
then it should also be decoupled to AV
SS
locally.
The negative supply rail for the analogue on-
chip blocks.
Internally generated bias voltage of
approximately AV
DD
/2, except when the device
is in Powersave or 'Zero-Power' modes, when
V
BIAS
will discharge to AV
SS
. This pin should be
decoupled to AV
SS
by a capacitor mounted
close to the device pins.
The inverted output of the Tx Output Buffer.
The non-inverted output of the Tx Output Buffer.
Description
6
7
8
DV
SS
RD
RT
Power
I/P
BI
9
RESETN
I/P
10
11
RXAFB
RXBN
O/P
I/P
12
13
RXAN
RXA
I/P
I/P
14
15
AV
SS
V
BIAS
Power
O/P
16
17
TXAN
TXA
O/P
O/P
©
2001 Consumer Microcircuits Limited
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D/866/1
V.22 bis Modem with AT Commands
CMX866
CMX866
D1/D6
18
Signal
AV
DD
Power
Description
The positive supply rail for the analogue on-chip
blocks. Levels and thresholds within the device
are proportional to this voltage.
The inverted DCD signal used for an RS232
interface with a Level Converter.
The inverted DSR signal used for an RS232
interface with a Level Converter.
The inverted CTS signal used for an RS232
interface with a Level Converter.
The inverted DTR signal used for an RS232
interface with a Level Converter.
The inverted RTS signal used for an RS232
interface with a Level Converter.
The non-inverted TD signal used for an RS232
interface with a Level Converter. This pin
accepts data from the external host µC for
transmission over the phone line.
The non-inverted RD signal used for an RS232
interface with a Level Converter. This pin sends
data to the external host µC which was received
over the phone line.
An auxiliary pin to force the CMX866 into
Command Mode from Data Mode and remain
off-hook. The ATO command will return the
CMX866 to Data Mode. This pin should be
connected to DV
SS
if not required.
The inverted RI signal used for an RS232
interface with a Level Converter. This is a 'wire-
ORable' output for connection to an external
host µC Interrupt Request input. This output is
pulled down to DV
SS
when active and is high
impedance when inactive. An external pullup
resistor is required (eg. R1 in Figure 2a).
The positive supply rail for the digital on-chip
blocks. Levels and thresholds within the device
are proportional to this voltage.
19
20
21
22
23
24
DCDN
DSRN
CTSN
DTRN
RTSN
TXD
O/P
O/P
O/P
I/P
I/P
I/P
25
RXD
O/P
26
ESC
I/P
27
RIN
O/P
28
DV
DD
Power
Notes:
I/P
O/P
BI
T/S
NC
=
=
=
=
=
Input
Output
Bidirectional
3-state Output
No Connection
©
2001 Consumer Microcircuits Limited
5
D/866/1
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