CML Microcircuits
COMMUNICATION SEMICONDUCTORS
CMX866
V.22 bis Modem
with AT Commands
D/866/4 January 2004
Provisional Issue
Features
Applications
• V.22 bis, V.22 and Bell 212A QAM/DPSK
• Telephone Telemetry Systems
• V.23, Bell 202, V.21 and Bell 103 FSK
• Remote Utility Meter Reading
• Integral AT Command Set with 'Fast Connect'
• Security Systems
• V.23 and Bell 202 'Fast Turnaround'
• Industrial Control Systems
• Support for Type 1 Caller Line Identification
• Electronic Cash Terminals / ATMs
• DTMF/Programmable Tones: Transmit and Receive
• Pay-Phones
• 'Zero-Power' and Powersave Standby Modes
• Cable TV Set-Top Boxes
• Low Power Operation
• 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 device is also able to detect off-hook parallel phones by monitoring voice activity on the line.
The CMX866 takes 5mA (typ.) from a single 2.7–5.5V supply and comes in 28-pin SSOP/SOIC
packages.
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CMX866
CONTENTS
Section
Page
1.1
Brief Description..................................................................................1
1.2
Block Diagram .....................................................................................3
1.3
Signal List ............................................................................................4
1.4
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
1.5
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 .............................................................................. 30
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
1.6
Application Notes .............................................................................. 37
1.6.1 Hardware Interface ................................................................ 37
1.6.2 Calling Modem AT Commands............................................. 42
1.6.3 Answering Modem AT Commands....................................... 42
1.6.4 RS232 Transaction Sequence .............................................. 43
1.7
Performance Specification................................................................ 44
1.7.1 Electrical Performance.......................................................... 44
1.7.1.1 Absolute Maximum Ratings ..................................... 44
1.7.1.2 Operating Limits ....................................................... 44
1.7.1.3 Operating Characteristics ........................................ 45
1.7.2 Packaging.............................................................................. 51
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1.2
CMX866
Block Diagram
Figure 1 Block Diagram
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1.3
CMX866
Signal List
CMX866
D1/D6
Signal
Description
Pin No.
Name
Type
1
XTALN
O/P
The output of the on-chip Xtal oscillator inverter.
2
XTAL/CLOCK
I/P
The input to the oscillator inverter from the Xtal
circuit or external clock source.
3
N/C
~
Reserved for future use. Connect this pin to
DVSS.
4
N/C
~
Reserved for future use. Connect this pin to
DVSS.
5
RDRVN
O/P
Relay drive output, low resistance pull down to
DVSS when active and medium resistance pull
up to DVDD when inactive.
6
DVSS
Power
The negative supply rail for the digital on-chip
blocks.
7
RD
I/P
Schmitt trigger input to the Ring signal detector.
Connect to DVSS if Ring Detector not used.
8
RT
BI
Open drain output and Schmitt trigger input
forming part of the Ring signal detector.
Connect to DVDD if Ring Detector not used.
9
RESETN
I/P
Schmitt trigger input to an active-low reset pin.
Connect to DVDD if no external reset signal
used
10
RXAFB
O/P
The output of the Rx Input Amplifier.
11
RXBN
I/P
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.
12
RXAN
I/P
The inverting input to the Rx Input Amplifier
13
RXA
I/P
The non-inverting input to the Rx Input
Amplifier. If this pin is to be connected to VBIAS
then it should also be decoupled to AVSS locally.
14
AVSS
Power
15
VBIAS
O/P
Internally generated bias voltage of
approximately AVDD /2, except when the device
is in Powersave or 'Zero-Power' modes, when
VBIAS will discharge to AVSS. This pin should be
decoupled to AVSS by a capacitor mounted
close to the device pins.
16
TXAN
O/P
The inverted output of the Tx Output Buffer.
17
TXA
O/P
The non-inverted output of the Tx Output Buffer.
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The negative supply rail for the analogue onchip blocks.
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CMX866
D1/D6
18
AVDD
Power
19
DCDN
O/P
The inverted DCD signal used for an RS232
interface with a Level Converter.
20
DSRN
O/P
The inverted DSR signal used for an RS232
interface with a Level Converter.
21
CTSN
O/P
The inverted CTS signal used for an RS232
interface with a Level Converter.
22
DTRN
I/P
The inverted DTR signal used for an RS232
interface with a Level Converter.
23
RTSN
I/P
The inverted RTS signal used for an RS232
interface with a Level Converter.
24
TXD
I/P
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.
25
RXD
O/P
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.
26
ESC
I/P
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 DVSS if not required.
27
RIN
O/P
The inverted RI signal used for an RS232
interface with a Level Converter. This is a 'wireORable' output for connection to an external
host µC Interrupt Request input. This output is
pulled down to DVSS when active and is high
impedance when inactive. An external pullup
resistor is required (eg. R1 in Figure 2a).
28
DVDD
Power
The positive supply rail for the digital on-chip
blocks. Levels and thresholds within the device
are proportional to this voltage.
Signal
Description
The positive supply rail for the analogue on-chip
blocks. Levels and thresholds within the device
are proportional to this voltage.
Notes:
I/P
O/P
BI
T/S
NC
=
=
=
=
=
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Input
Output
Bidirectional
3-state Output
No Connection
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1.4
CMX866
External Components
C1, C2
R1
X1
22pF
100kΩ
11.0592MHz
C3, C4, C6
C5, C7
L1, L2
100nF
10uF
100nH
(optional)
Resistors ±5%, capacitors ±20% unless otherwise stated.
Figure 2a Recommended External Components for Typical Application
This device is capable of detecting and decoding small amplitude signals. To achieve this DVDD, AVDD
and VBIAS should be decoupled and the receive path protected from extraneous in-band signals. It is
recommended that the printed circuit board is laid out with both AVSS and DVSS ground planes in the
CMX866 area, as shown in Figure 2b, with provision to make a link between them close to the CMX866.
To provide a low impedance connection to ground, the decoupling capacitors (C3 – C7) must be mounted
as close to the CMX866 as possible and connected directly to their respective ground plane. This will be
achieved more easily by using surface mounted capacitors.
VBIAS is used as an internal reference for detecting and generating the various analogue signals. It must
be carefully decoupled, to ensure its integrity. Apart from the decoupling capacitor shown (C3), no other
loads are allowed. If VBIAS needs to be used to set external analogue levels, it must be buffered with a
high input impedance buffer.
The DVSS connections to the Xtal oscillator capacitors C1 and C2 should also be of low impedance and
preferably be part of the DVSS ground plane to ensure reliable start up of the oscillator.
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Figure 2b Recommended Power Supply Connections and De-coupling
ANALOGUE
C3, C6
C7
L2
Note:
DIGITAL
100nF
10uF
100nH
(optional, see note)
C4
C5
L1
100nF
10uF
100nH
(optional, see note)
The inductors L1 and L2 and the electrolytic capacitor C7 can be omitted without significantly
degrading the system performance.
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1.4.1
CMX866
Ring Detector Interface
Figure 3 shows how the CMX866 may be used to detect the large amplitude Ringing signal voltage
present on the 2-wire line at the start of an incoming telephone call.
The ring signal is usually applied at the subscriber's exchange as an ac voltage inserted in series with
one of the telephone wires and will pass through either C20 and R20 or C21 and R21 to appear at the top
end of R22 (point X in Figure 3) in a rectified and attenuated form.
The signal at point X is further attenuated by the potential divider formed by R22 and R23 before being
applied to the CMX866 RD input. If the amplitude of the signal appearing at RD is greater than the input
threshold (Vthi) of Schmitt trigger 'A' then the N transistor connected to RT will be turned on, pulling the
voltage at RT to DVSS by discharging the external capacitor C22. The output of the Schmitt trigger 'B'
will then go high, setting bit 14 (Ring Detect) of the DSP Status Register. The on-chip µController will
then respond by setting pin RIN low.
The minimum amplitude ringing signal that is certain to be detected is:
( 0.7 + Vthi x [R20 + R22 + R23] / R23 ) x 0.707 Vrms
where Vthi is the high-going threshold voltage of the Schmitt trigger A (see section 1.7.1).
With R20-22 all 470kΩ as Figure 3, setting R23 to 68kΩ will guarantee detection of ringing signals of
40Vrms and above for DVDD over the range 3 to 5V.
R20, 21, 22
R23
R24
C20, 21
C22
D1-4
470kΩ
See text
470kΩ
0.1µF
0.33µF
1N4004
Resistors ±5%, capacitors ±20%
Figure 3 Ring Signal Detector Interface Circuit
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If the time constant of R24 and C22 is large enough then the voltage on RT will remain below the
threshold of the 'B' Schmitt trigger for the duration of a ring cycle. The time for the voltage on RT to
charge from DVSS towards DVDD can be derived from the formula:
VRT = DVDD x [1 - exp(-t/(R24 x C22)) ]
As the Schmitt trigger high-going input threshold voltage (Vthi) has a minimum value of 0.56 x DVDD,
then the Schmitt trigger B output will remain high for a time of at least 0.821 x R24 x C22 following a
pulse at RD. The values of R24 and C22 given in Figure 3 (470kΩ and 0.33µF) give a minimum RT
charge time of 100msec, which is adequate for ring frequencies of 10Hz or above.
Note that this circuit will also respond to a telephone line voltage reversal. The external host µC can
distinguish between a Ring signal and a line voltage reversal by measuring the time that pin RIN is low.
If the Ring detect function is not used then pin RD should be connected to DVSS and RT to DVDD.
1.4.2
Line Interface
A line interface circuit is needed to provide dc isolation and to terminate the line.
2-Wire Line Interface
Figure 4a shows a simplified interface for use with a 600Ω 2-wire line. The complex line termination is
provided by R13 and C10, high frequency noise is attenuated by C10 and C11, while R11 and R12 set
the receive signal level into the modem. For clarity the 2-wire line protection circuits and the connection
to RXBN (for on-hook CLI applications) have not been shown.
R11
R12
R13
See text
100kΩ
600Ω
C3
C10
C11
See Figure 2
33nF
100pF
Resistors ±5%, capacitors ±20%
Figure 4a 2-Wire Line Interface Circuit
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The transmit line signal level is determined by the voltage swing between the TXA and TXAN pins, less
6dB due to the line termination resistor R13, and less the loss in the line coupling transformer. Allowing
for 1dB loss in the transformer, then with the DSP Tx Mode Register set for a Tx Level Control gain of
0dB (S25 register set to 'xxxxx111') the nominal transmit line levels will be:
QAM, DPSK and FSK Tx modes (no guard tone)
Single tone transmit mode
DTMF transmit mode
AVDD = 3.0V
-10dBm
-10dBm
-6 and -8 dBm
AVDD = 5.0V
-5.5dBm
-5.5dBm
-1.5 and -3.5 dBm
For a line impedance of 600Ω, 0dBm = 775mVrms. See also section 1.7.1.3
In the receive direction, the signal detection thresholds within the CMX866 are proportional to AVDD and
are affected by the Rx Gain Control gain setting in the DSP Rx Mode Register (as indicated by the value
held in the S26 register). The signal level into the CMX866 is affected by the line coupling transformer
loss and the values of R11 and R12 of Figure 4a.
Assuming 1dB transformer loss, the Rx Gain Control programmed to 0dB (S26 register set to 'xxxxx111')
and R12 = 100kΩ, then for correct operation (see section 1.7.1.3) the value of R11 should be equal to:
500 / AVDD kΩ i.e. 160kΩ at 3.0V, falling to 100kΩ at 5.0V
When the RDRVN pin is high impedance (= on-hook = inactive) the auxiliary receive input pin RXBN is
internally connected to the RXAN pin. This can be used to increase the Rx gain (required for Type 1
Caller Line Identification reception) by reducing the effective value of R11, as shown in Figures 11 and
12. When the RDRVN pin is low (= off-hook = active) the RXBN pin is not connected.
4-Wire Line Interface
Figure 4b shows an interface for use with a 600Ω 4-wire line. The line terminations are provided by R10
and R13, high frequency noise is attenuated by C11 while R11 and R12 set the receive signal level into
the modem. Transmit and receive line level settings and the value of R11 are as for the 2-wire circuit.
R10, 13
R11
R12
C3
C11
C12
600Ω
See text
100kΩ
See Figure 2
100pF
33nF
Resistors ±5%, Capacitors ±20%
Figure 4b 4-Wire Line Interface Circuit
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1.4.3
CMX866
Serial Interface
The CMX866 is controlled by sending AT commands over the serial interface from an external host µC.
For simplicity, an asynchronous protocol has been adopted: 9600 baud, 8-bit words, no parity, 1 stop-bit.
Since this communications rate exceeds that over the phone line, it is necessary to use CTS flow control
to moderate the data rate, so that on average it equals the baud rate for the communications standard
adopted. The CTS flow control method provided on the CMX866 will also work with the RTS/CTS
handshake protocol used by some µControllers. AT commands and phone numbers need to be stored
for future use and the CMX866 provides four internal buffers for phone number and command storage
and for data buffering (see Figure 5a).
When the external host µC is ready to transmit AT commands or data it should take the Request To Send
signal active (RTSN pin goes low) and place the information to be sent on the Transmit Data (TXD) pin.
When the CMX866 is ready to accept this information from the external host µC it will take the Clear To
Send signal active (CTSN pin goes low). The information should be sent as 8-bit bytes, encapsulated by
a start bit (low) and a stop bit (high). The CMX866 should be presented with continuous mark (stop bits)
when the host µC has no information to send. As each byte is received it is stored in a 48-byte AT
command buffer when in Command mode or in a 16-byte receive data buffer when in Data Transfer
mode. The CMX866 will take the CTSN pin high when either buffer is full and will ignore further
information on the TXD pin until the on-chip µController in the CMX866 is ready to accept it. At this time,
the CMX866 will once again take the CTSN pin low to signify its readiness to accept more information,
providing the RTSN pin is already low. If the external host µC does not have an 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 from the host µC to the CMX866, but data flow from the
CMX866 to the host µC is allowed. As the incoming AT command is being interpreted, any phone
number is identified and stored separately in the 24-byte phone number buffer.
When the CMX866 is in Data Transfer mode and it receives a signal from the phone line which exceeds
the minimum amplitude threshold, it will attempt to demodulate the signal and place the received data on
the RXD pin. At the same time it will make the Data Carrier Detected signal active (DCDN pin goes low).
Received data is presented to the RXD pin at 9600 baud (with the same protocol as for transmission,
regardless of the format that was used over the phone line), after a complete byte has been
demodulated. There is a 24-byte message buffer in the 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 host µC 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 CMX866 is not in Data Transfer mode, the DCDN and RXD pins
will be taken high.
If the CMX866 receives a RING signal on the RD and RT pins, such that the detection threshold is
exceeded, then the device will forward this condition to the external host µC by taking the 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 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 DSRN and DTRN pins do not act as a handshake with the external host µC. The DSRN pin indicates
the operational status of the on-chip µController (low = ready to communicate with an external host µC).
The DTRN pin is used for taking the CMX866 out of a Powersave or 'Zero-Power' state. It 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 host µC 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 is taken high at any time whilst the CMX866 is in
Data Transfer mode, a fixed, 100ms timeout is started. On completion of the timeout, the CMX866 will
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return to Command mode, enabling further AT commands to be sent. If the DTRN pin goes high whilst
the CMX866 is in 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 CMX866 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 is taken high at any time whilst the CMX866 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
CMX866 will return to Command mode and take CTSN high. If the RTSN pin goes high whilst the
CMX866 is in 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.
1.4.4
RESETN pin
The CMX866 has an internal power-up reset function which is activated whenever power is first applied to
the device. 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 onchip µController into an operating state. This internal power-up reset function is OR-ed with the RESETN
pin. The state of the CMX866, including its outputs, is undefined for approximately 4.7ms, until this reset
operation is complete.
When the RESETN pin is taken low, the on-chip µcontroller is reset and its program counter held at
address $0000. It remains in this condition until the RESETN pin is taken high, at which time the software
reset operation described above is performed. The RESETN pin must be held low for at least 5.0µs.
When the CMX866 first enters the operating state, it reports its configuration as follows:
•
CMX866 waits for DTRN to go active (low)
•
CMX866 takes the DSRN pin active (low) to indicate its readiness to
communicate with an external host µC
•
CMX866 waits for RTSN to go active (low)
•
CMX866 sends "CMX866" identification message to external host µC
(equivalent to the host µC 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 host µC. If not successful, CMX866 sends "DSP Error" message to the
external host µC. 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 went low
•
CMX866 takes the CTSN pin active (low) to indicate its readiness to
communicate with an external host µC
Note that the on-chip µController does not perform its own internal diagnostic self-check as this
is not considered necessary.
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1.5
General Description
1.5.1
Internal Structure
CMX866
Internally, the CMX866 consists of a dedicated DSP which is controlled by an on-chip µController. This
µController is preprogrammed to interpret the AT commands provided by the user into instructions for
controlling the dedicated DSP. It also handles the CMX866 power management and other functions. The
DSP is preprogrammed with algorithms to implement the various modem functions, but also has Tone
Generators and Detectors which are user programmable with AT commands, via the on-chip µController.
The CMX866's DSP transmit and receive operating modes are independently programmable by means of
AT commands which write values into the S-Registers. The on-chip µController then interprets the
values in these registers and programs the corresponding registers in the dedicated DSP.
The DSP transmit mode can be set to any one of the following:
• V.22 bis modem. 2400bps QAM (Quadrature Amplitude Modulation)
• V.22 and Bell 212A modem. 1200 bps DPSK (Differential Phase Shift Keying)
• V.21 modem. 300bps FSK (Frequency Shift Keying)
• Bell 103 modem. 300bps FSK
• V.23 modem. 1200 or 75 bps FSK
• Bell 202 modem. 1200 or 150 bps FSK
• DTMF transmit
• Single tone transmit (from a range of modem calling, answer and other tone frequencies)
• User programmed tone or tone pair transmit (programmable frequencies and levels)
• Disabled
The DSP receive mode can be set to any one of the following:
• V.22 bis modem. 2400bps QAM
• V.22 and Bell 212A modem. 1200 bps DPSK
• V.21 modem. 300bps FSK
• Bell 103 modem. 300 bps FSK
• V.23 modem. 1200 or 75 bps FSK
• Bell 202 modem. 1200 or 150 bps FSK
• DTMF detect
• 2100Hz and 2225Hz answer tone detect
• Call progress signal detect
• Dual alert tone pair detect (for Caller Line Identification)
• User programmed tone or tone pair detect
• Disabled
The CMX866 can also be set into 'Zero-Power' or Powersave states, which disable all circuitry except for
the Ring Detector. The S-Register settings and the CMX866's configuration are remembered when in
'Zero-Power' or Powersave states. The 'Zero-Power' state stops the crystal oscillator and removes power
from the VBIAS pin, for minimum power consumption. It takes about 30ms for the CMX866 to become
operational from the 'Zero-Power' state. The Powersave state stops the internal clock distribution, but
retains power to the crystal oscillator and VBIAS circuit. Consequently, the CMX866 can become
operational from this state in about 10µs. If the TXD pin is tied to the DTRN pin (to implement a reduced
RS232 interface) any activity on the TXD pin will also take the CMX866 into an operational state. In this
case, however, data may be corrupted until the CMX866 is fully operational.
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1.5.2
CMX866
Operating States and Data Flow
The following diagram shows the flow of data in the CMX866:
Figure 5a CMX866 Data Flow Diagram
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CMX866
The following state transition chart shows the various modes of operation for the CMX866:
Figure 5b CMX866 State Transition Chart
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1.5.3
CMX866
Functional Description
The CMX866 is a multi-functional integrated modem chip which requires simple telephone line and
RS232 interfaces to implement a complete, low-power modem that can be controlled by widely used AT
commands. A list of the main features of this product is given below:
Function
Commands
Registers
• Set modem line communication functions, software protocol
and control characters for AT commands
Bn, &Gn
S2, S3, S4, S5, S10,
S23, S24, S27
• Select automatic or no fallback from V.22bis to V.22
Nn
S24
• Select V.23 or Bell 202 fast turnaround
RO
S14, S24
• Return to Command mode by:
1) Issuing an escape sequence: <delay> +++ <delay>
2) Taking the DTRN pin high (active low)
3) Taking the ESC pin high (active high)
4) Taking the RTSN pin high (active low)
S12
S24
S14
S28
• Bypass the answertone detection sequence to give "Fast
Connect"
S14
• Set modem into answer or originate mode, independently of
whether a call is being initiated or answered
S14
• Detect dual alert tones or FSK whilst on-hook (for Type 1 CLI)
@Rn, @RR,
@F8
• Place the CMX866 into either 'Zero-Power' or Powersave
states. When in these states, the CMX866 can be "woken-up"
by either:
1) activity on the DTRN pin (including transmitted data, if this
is also wired to the DTRN pin)
2) detection of a Ringing condition on the RD and RT pins
&Z0, &Z1
S21
• Make local and remote digital loopback connections and allow
remote modems to digitally loopback the CMX866. This
facilitates the provision of loopback tests by the external host
µController
&Tn
S15, S16, S18, S21
• Automatically dial a directory number and monitor call
progress tones before entering the modem function
Dn, DTn, DL,
Hn, Xn
S6, S7, S8, S11,
S22, S29
• Automatically answer an incoming call
A, Hn
S0, S1, S17
• Independently set the Rx and Tx path gain
S25, S26
• Perform internal confidence tests on the CMX866 and report
back the device revision, status and configuration
In, &V
• Perform miscellaneous line communications functions, such as
repeating the last command, selecting alphabetic or numeric
result codes, etc.
A/, En, Qn,
Vn
• Restore the default 'factory profile', placing the CMX866 into a
known state without resetting the device
Z
• Set the serial interface (RS232) communications protocol and
CMX866 hardware configurations
&Cn, &Dn
• Enter Data mode from Command mode
O, RO, &Tn
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S14
S24
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1.5.4
CMX866
AT Command and Register Set
1.5.4.1 AT Command and S-Register Summary
AT Command
Parameters
A
A/
Bn
Dn ... n
or DTn ... n
Function
Default
Answer Command - Answer and establish a connection when off-hook
Re-execute last command
n = 0..9
Select Communications Standard
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
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
n=1
Go online in Data mode (from Command mode)
n = 0,1
Sn?
n = 0..29
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
S-Register "n" Read - Display specified S Register contents
Sn=x
n = 0..29
S-Register "n" Write - Write to specified S Register
Vn
Xn
Z
n =0,1
n = 0..3
Return result codes as numbers (n=0) or words (n=1)
Calling and Response Characteristics
Restore factory profile for CMX866
n=0
n=3
&Cn
n = 0,1
DCD always on (n=0) or DCD follows carrier (n=1)
n=1
&Dn
&Gn
&Tn
n= 0..2
n = 0..2
n = 0,3..6
DTR signal procedure
Guard Tone Select - Disable (n=0), Enable 550Hz (n=1) or 1800Hz (n=2)
User accessible Loopback Tests and Diagnostics
n=2
n=0
n=0
RO
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
S Registers
Parameters
S0
0…255
Function
Number of rings before answering, 0 = Auto-answer disabled
S1
0…255
Number of rings received
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
S10
1…255
Lost carrier to hang up delay in units of 100ms
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Default
2
0
+
17
CR
700ms
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CMX866
S Registers
Parameters
S11
5…255
DTMF tone duration and interdigit pause duration in units of 10ms
S12
0…255
Escape code guard time in units of 50ms
S13
Function
Default
100ms
1s
Reserved
S14
0…255
General Options
S15
0…255
Loopback carrier off time in units of 10ms
80ms
S16
0…255
Drop time for loopback in units of 10ms
60ms
S17
0…255
Handshake timeout (Answering) in seconds
30s
S18
0…255
Loopback timer (0= no timeout) in seconds
0s
S19
$92
Reserved for test functions
S20
Reserved
S21
0…255
Loopback and Power states
$10
S22
0…255
Calling and response characteristics selection
$C0
S23
0…255
Guard tone selection
$00
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 units of 10ms
Bn Register
Parameter
Communications Protocol
n
Xn Register
Fallback
(Mapped to S27 register)
0
V.22bis 2400bps QAM
1
V.22 1200bps DPSK
2
V.23 Tx 75bps, Rx 1200bps (Master)
3
V.23 Tx 1200bps, Rx 75bps (Slave)
4
Reserved
5
V.21 300bps FSK
6
Bell 212A 1200bps DPSK
7
Bell 202 Tx 150bps Rx 1200bps
8
Bell 202 Tx 1200bps Rx 150bps
9
Bell 103 300bps FSK
V.22
Parameter
Calling and Response Characteristics
n
0
(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
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&Dn Register
&Gn Register
CMX866
Parameter
DTR action
n
(Mapped to S24 register)
0
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
(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
1.5.4.2 General Description of AT Commands
Only the AT commands listed above are supported. Valid commands will generate an 'OK' result code
(see section 1.5.4.6) and invalid commands will be rejected with an 'ERROR' result code, when command
echoing and word result codes are enabled. The on-chip µController will send a <LF> character directly
after a <CR> character to ensure compatibility with external host 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.
Every line of commands (except for A/ and the escape sequence) must begin with the AT prefix and be
terminated with a carriage return <CR>. The on-chip µController 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 on-chip µController 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 CMX866 in the order in which they are sent by the external host µC.
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: eg ATS0=<CR> is equivalent to ATS0=0<CR>.
Receipt of a back space will cause the CMX866 to send a "back space, space, back space" sequence of
characters to the external host µC, 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.
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CMX866
The escape sequence ‘+++’ (with Guard Time = 1s [see S12 register] before and after the sequence) will
cause the CMX866 to enter Command mode from Data Transfer mode and to return an ‘OK’ response.
1.5.4.3 AT Commands in Detail
Command
Description
A
Answer Command
The CMX866 will go off-hook and attempt to answer an incoming call by
establishing a connection with a remote modem. The command is not valid if there
is no incoming call and it will return the 'ERROR' result code.
Syntax: ATA<CR>
A/
Re-Execute Previous Command Line
Re-executes the last issued command line. This command does not require the AT
prefix or a carriage return. If the last issued command line contained several AT
commands, each of these will be repeated.
Syntax: A/
Bn
Select Communications Standard
Selects the communications standard specified by the parameter n.
Syntax: ATBn<CR>
Modifier Usage
n=0 Selects ITU-T V.22bis at 2400bps QAM (default).
n=1 Selects ITU-T V.22 at 1200bps DPSK.
n=2 Selects ITU-T V.23 with Tx 75bps and Rx 1200bps FSK.
n=3 Selects ITU-T V.23 with Tx 1200bps and Rx 75bps FSK.
n=4 Reserved for future use.
n=5 Selects ITU-T V.21 at 300bps FSK.
n=6 Selects Bell 212A at 1200bps DPSK.
n=7 Selects Bell 202 with Tx 150bps and Rx 1200bps FSK.
n=8 Selects Bell 202 with Tx 1200bps and Rx 150bps FSK.
n=9 Selects Bell 103 at 300bps FSK.
Dn
or DTn
Dial Command
This command directs the CMX866 to go off-hook, dial the directory number
entered and attempt to establish a connection with a remote modem by going into
Data Transfer mode. The n represents an ASCII string composed of dial digits and
dial modifiers and must not exceed the 23 character buffer limit. The DTMF tone
dialling digits include 0 through 9, A, B, C, D, and the symbols # and *. Loopdisconnect (pulse) dialling is not implemented.
For example: ATD9,01621875500<CR>
Modifier Usage
n=L Re-dial last number.
n=,
Delay dial sequence (pause setting contained in S8 register).
n=!
Send a timed break recall (duration in S29 register).
n=;
Remain in command mode after dialling, no handshake.
En
Echo Command Characters
Syntax: ATEn<CR>
Modifier Usage
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CMX866
n=0 Disables the echoing of commands to the external host µC.
n=1 Enables echoing of commands to the external host µC (default).
Hn
Hook Switch Control
Syntax: ATHn<CR>
Modifier Usage
n=0 Instructs the CMX866 to go on-hook (RDRVN pin goes high). This disconnects
the CMX866 from the line (default).
n=1 Instructs the CMX866 to go off-hook (RDRVN pin goes low).
Line disconnection also occurs if the CMX866 is placed in 'Zero-Power' or
Powersave mode, if the RESETN pin is taken low or, in certain cases, if the DTRN
pin is taken high (see &Dn command).
In
Identification
Requests the CMX866 to return its product identification information.
Syntax: ATIn<CR>
Modifier Usage
n=0 Displays the product identification:
Nn
"CMX866"
Modulation Fallback Option
Syntax: ATNn<CR>
Modifier Usage
n=0 When originating or answering, the CMX866 negotiates only at the specified
communications standard.
n=1 When originating or answering, the CMX866 falls back from V.22bis to V.22,
as required (default).
O
Change to Data Transfer Mode
Used during on-line AT Command mode, this command changes the CMX866
operation to Data Transfer mode, without initiating any retrain sequence.
Syntax: ATO<CR>
Qn
Enable/Disable Modem Responses
Syntax: ATQn<CR>
Modifier Usage
n=0 Enables result codes. Codes are issued to the external host µC (default).
n=1 Disables result codes. Codes are not issued to the external host µC.
RO
Change to Data Transfer Mode in Reverse Direction
Used during on-line AT Command mode to execute a V.23 turnaround if enabled
(see S14 and S24 registers), then returns to Data Transfer mode, like the O
command above.
Syntax: ATRO<CR>
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Sn?
CMX866
S-Register Read
Command for displaying the contents of an S-Register (See S-Register Table).
Syntax: ATSn?<CR>
where n is the S-Register to be interrogated (decimal).
Value returned is either in decimal or hex (default) format depending on the setting
of Bit 4 in the S14 register. Note that a ? command on its own is invalid.
Sn=x
S-Register Write
Command for writing to an S-Register (See S-Register Table).
Syntax: ATSn=x<CR>
where n is the S-Register (decimal) and x is the value to be written (decimal, 0255). Note that a =x command on its own is invalid.
Vn
Result Code Format
Syntax: ATVn<CR>
Modifier Usage
n=0 Instructs the CMX866 to display result codes as numbers (default).
n=1 Instructs the CMX866 to display result codes as words.
Xn
Calling Characteristics
Determines which set of responses and calling characteristics are used.
Syntax: ATXn<CR>
Modifier Usage
n=0 The CMX866 will ignore dial tones and busy tones. Dial tone wait time is zero,
and blind dialling is enabled after the delay in register S6. The CMX866 returns a
CONNECT xxxx result code when a connection is established, where xxxx is the
Tx/Rx line speed, otherwise it returns a NO CARRIER result code.
n=1 The CMX866 waits for a dial tone before dialling but will ignore busy tone. If a
dial tone is not detected within the time in register S6, a NO DIAL TONE result
code is returned. The CMX866 returns a CONNECT xxxx result code when a
connection is established, where xxxx is the Tx/Rx line speed, otherwise it returns
a NO CARRIER result code.
n=2 The CMX866
code is returned.
CMX866 returns a
where xxxx is the
code.
will ignore dial tone. If busy tone is detected, a BUSY result
Blind dialling is enabled after the delay in register S6. The
CONNECT xxxx result code when a connection is established,
Tx/Rx line speed, otherwise it returns a NO CARRIER result
n=3 If a dial tone is not detected within the time in register S6, a NO DIAL TONE
result code is returned. If a busy tone is detected, a BUSY result code is returned.
The CMX866 returns a CONNECT xxxx result code when a connection is
established, where xxxx is the Tx/Rx line speed, otherwise it returns a NO
CARRIER result code (default).
Z
Factory Reload
Reloads the factory default S-Register settings (See S-Register Table).
Syntax: ATZ<CR>
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CMX866
1.5.4.4 Extended AT Commands
Command
&Cn
Description
Carrier Detect
Determines the action of the DCDN pin.
Syntax: AT&Cn<CR>
Modifier Usage
n=0 DCD is always on (DCDN pin is held permanently low).
n=1 DCD follows the received carrier. If a carrier is present on the line, then DCD
is on (DCDN pin is held low). Otherwise DCD is off (DCDN pin is held high)
(default).
&Dn
Data Terminal Ready
Determines the meaning of the DTRN pin.
Syntax: AT&Dn<CR>
Modifier Usage
n=0 DTRN pin is ignored
n=1 When an on to off transition of DTR occurs (DTRN pin goes from low to high),
the CMX866 goes into Command mode (if it was in Data Transfer mode), after a
fixed delay of 100ms, during which time the transition is qualified. Whilst in
Command mode, if DTRN remains high for more than 500ms, then the CMX866
goes on-hook.
n=2 Same as above (n=1), except that the CMX866 also goes on-hook when the
DTRN transition is qualified.
&Gn
Guard Tone Select
Selects the Guard tone to be transmitted with highband QAM or DPSK.
Syntax: AT&Gn<CR>
Modifier Usage
n=0 Disable guard tone (default).
n=1 Enable 550Hz guard tone.
n=2 Enable 1800Hz guard tone.
&Tn
Loopback Connection
Instructs the CMX866 to make local or remote loopback connections, or to action a
remote request to make loopback connections.
Syntax: AT&Tn<CR>
Modifier Usage
n=0 Remove all loopbacks and return to Data Transfer mode.
n=1 Reserved.
n=2 Reserved.
n=3 Make a local digital loopback connection to loopback the received data stream
from the remote modem.
n=4 Enable remote requests for a local digital loopback connection.
n=5 Disable remote requests for a local digital loopback connection.
n=6 Request a remote digital loopback connection.
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CMX866
Note that if the CMX866 is in Data Transfer mode, an escape sequence must be
issued (+++) to return the CMX866 to Command mode before this loopback
connection command can be given. The AT&T0, AT&T3 and AT&T6 commands
can only be issued when off-hook. The AT&T4 and AT&T5 commands can be
issued when either on-hook or off-hook.
&V
Current Configuration
Returns the current CMX866 configuration by reading the S-Registers. The register
data is output on the RXD pin in the form (where xxx is decimal data):
S00: xxx S01: xxx S02: xxx S03: xxx S04: xxx S05: xxx S06: xxx S07: xxx S08: xxx S09: xxx<CR>
S10: xxx S11: xxx S12: xxx S13: xxx S14: xxx S15: xxx S16: xxx S17: xxx S18: xxx S19: xxx<CR>
S20: xxx S21: xxx S22: xxx S23: xxx S24: xxx S25: xxx S26: xxx S27: xxx S28: xxx S29: xxx<CR>
This register data is also available in hexadecimal form, by setting bit 4 of S14
register.
Syntax: AT&V<CR>
&Zn
Sleep States
Instructs the CMX866 to enter one of the following sleep states:
Syntax: AT&Zn<CR>
Modifier Usage
n=0 'Zero-Power' state.
n=1 Powersave state.
The 'Zero-Power' state stops the crystal oscillator and removes power from the
VBIAS pin, for minimum power consumption. It takes about 30ms for the CMX866
to become fully operational from the 'Zero-Power' state. However, the crystal
oscillator only takes about 1.4ms to become stable, so commands which do not
require the analogue parts of the DSP to be stable (VBIAS at ½VDD) can be given to
the on-chip µController after this time.
The Powersave state stops the internal clock distribution, but retains power to the
crystal oscillator and VBIAS circuit. Consequently, the CMX866 can become
operational from this state in about 10µs.
To enter either sleep state, the DTRN pin must already be inactive (high) and the
RD and RT pins inactive (low).
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CMX866
1.5.4.5 S-Registers
The following table gives a more detailed description of the available S-Registers and their functions.
The register range, units and default values are also listed.
S-Register
Description
Reg
Range
Units
S0
0-255
Rings
Automatic answer - Number of rings until automatic
answer. If the register is zero the modem will not
automatically answer.
Default
2
S1
0-255
Rings
Count incoming rings - This register is read only and
contains the number of rings detected by the CMX866.
0
S2
0-127
ASCII
Decimal
Escape character value - Contains the ASCII decimal
value of the escape character. The default setting is an
ASCII + and the escape sequence is +++. A value over
127 disables the escape sequence.
43
S3
0-127
ASCII
Decimal
Carriage return character - Contains the ASCII decimal
value of the character recognised as the command line
terminator. This character will also be sent at the end of
result codes. The default setting is <CR>.
13
S4
0-127
ASCII
Decimal
Line feed character - Contains the ASCII decimal value
of the character recognised as a line feed. This
character is ignored if present in a command string. The
default setting is <LF>. The CMX866 sends the line feed
character after a carriage return only when word
responses are sent.
10
S5
0-127
ASCII
Decimal
Backspace character - Contains the ASCII decimal
value of the character recognised as a backspace. The
default setting is <BS>.
8
S6
2-255
1s
Wait time for blind dialling - If Blind Dialling is enabled
(see Xn command, Register S22), sets the length of time
to pause after the CMX866 goes off-hook before dialling
the first digit of the directory number.
4
If Blind Dialling is disabled, sets the length of time to wait
for a dial tone after the CMX866 goes off-hook. If a dial
tone is not received in this time, an 'ERROR' result code
is returned.
S7
1-255
1s
Wait for carrier after dial - Sets the length of time the
CMX866 waits for a carrier before returning on-hook.
50
S8
0-255
1s
Pause Time for Comma Dial Modifier - Specifies the
number of seconds to pause for each comma (,)
encountered in a dial string.
2
S9
1-255
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Reserved
25
D/866/4
V.22 bis Modem with AT Commands
CMX866
S-Register
Description
Reg
Range
Units
S10
1-255
100ms
Lost carrier to hang up delay - Sets the length of time
that the CMX866 waits before hanging up after the loss
of a carrier. This allows the CMX866 to distinguish
between disturbances that momentarily break the
connection and the remote modem hanging up.
7
S11
5-25
10ms
DTMF tone duration - Defines the duration of DTMF
tones for tone dialling. The length of pause between
each DTMF tone is the same as this duration time.
10
S12
0-255
50ms
Escape code guard time - Specifies the minimum time
of no data before and after entry of the escape
sequence.
20
S13
S14
0-255
0-255
Hex
S15
0-255
10ms
Loopback Carrier Off Time - To terminate a loopback
test at a remote modem, the CMX866 turns off the
carrier sent to that modem for the time specified in this
register.
8
S16
0-255
10ms
Drop Time for Loopback - If a loopback test is being
performed by a remote modem, detection of a drop in
the carrier from that modem which exceeds the time set
in this register will cause the local loopback to be
removed.
6
S17
0-255
1s
Handshake Timeout - If the handshake sequence, when
answering, exceeds this duration, the handshake will be
aborted and the modem will return to Command mode.
30
S18
0-255
1s
Loopback Timer - Defines the duration in seconds for
which the modem performs diagnostic tests. On timeout,
the test is terminated and the modem returns to
Command mode. The default value of 0s disables the
loopback timer, so that tests will run indefinitely. A test
can also be terminated from Command mode at any
time by issuing the AT&T0 command, which then returns
the modem to Data Transfer mode.
0
2004 CML Microsystems Plc
Reserved
General options - provides the following functions:
Bit 0 - V.23/Bell 202 Turnaround, 0 Disabled, 1 Enabled
Bit 1 - Echo command character, 0 Disables echoing
(ATE0), 1 Enables echoing (ATE1)
Bit 2 - Result code display, 0 Send responses (ATQ0),
1 Do not send responses (ATQ1)
Bit 3 - Word or number responses, 0 Send number
responses (ATV0), 1 Send word responses (ATV1)
Bit 4 - DSP or S-Register o/p format, 0 Decimal, 1 Hex
Bit 5 - Fast Connect, 0 Disabled, 1 Enabled
Bit 6 - ESC pin, 0 Disabled, 1 Enabled
Bit 7 - Answer/originate operation, 0 Answer (ATA),
1 Originate (ATD)
26
Default
92
D/866/4
V.22 bis Modem with AT Commands
CMX866
S-Register
Description
Reg
Range
S19
0-255
Units
Reserved – Reserved for test functions
S20
0-255
Reserved
S21
0-255
Hex
Loopback and Power States - controls the operation of
remote loopback and operational states:
Bit 4 - Remote loopback, 0 Disabled, 1 Enabled
(See &Tn command)
Bit 6 - Powersave state, 0 Not powersaved,
1 Powersaved
Bit 7 - 'Zero-Power' state, 0 Not 'Zero-Power',
1 'Zero-Power'
All other bits Reserved
10
S22
0-255
Hex
Calling and Response Characteristics (see section
1.5.4.1):
Bit 4-0 - Reserved
Bit 7-5 - Calling and Response Characteristics:
000 Ignore Dial Tone and Busy Tone (ATX0),
100 Ignore Busy Tone, wait for Dial Tone (ATX1),
101 Ignore Dial Tone, wait for Busy Tone (ATX2),
110 Wait for Dial Tone and Busy Tone (ATX3)
C0
S23
0-255
Hex
Guard Tone Selection (see section 1.5.4.1):
Bit 5-0 - Reserved
Bit 7-6 - Guard Tone Activity:
00 Disabled (AT&G0),
11 Enabled, guard tone = 550Hz (AT&G1)
10 Enabled, guard tone = 1800Hz (AT&G2)
00
S24
0-255
Hex
Equaliser, DCD and DTR status (see section 1.5.4.1):
Bit 0 - Reserved. Permanently set to 1
Bit 1 - Fixed Compromise Equaliser, 0 Enabled, 1
Disabled
Bit 2 - Auto-Equaliser, 0 Disabled, 1 Enabled
Bit 3 - DCDN pin function, 0 DCDN always low, 1
DCDN follows inverse of carrier
Bit 5-4 - DTRN pin function,
00 Ignore DTRN signal (AT&D0),
01 Go to Command mode when low to high
transition has been qualified (AT&D1)
10 Go on-hook then go to Command mode when
low to high transition has been qualified (AT&D2)
Bit 6 - Reserved for use with the V.23 or Bell 202
turnaround function (used by the ATRO command)
Bit 7 - Fallback mechanism from V.22bis to V.22
(equivalent to ATN1 command), 0 Disabled, 1
Enabled
A9
2004 CML Microsystems Plc
27
Default
D/866/4
V.22 bis Modem with AT Commands
CMX866
S-Register
Description
Reg
Range
Units
S25
0-255
Hex
Tx Gain, Tx data format on phone line:
Bit 2-0 - Tx Gain, 000 (-10.5dB) through to 111 (0dB)
in 1.5dB steps
Bit 5-3 - Tx Data/Stop bits:
000 (5 data, 1 stop),
001 (5 data, 2 stop),
010 (6 data, 1 stop),
011 (6 data, 2 stop),
100 (7 data, 1 stop),
101 (7 data, 2 stop),
110 (8 data, 1 stop) - default,
111 (8 data, 2 stop)
Bit 7-6 - Tx Data Format:
00 (start/stop mode - odd parity),
01 (start/stop mode - even parity),
10 (start/stop mode - no parity) - default,
11 (Synchronous mode)
B0
S26
0-255
Hex
Rx Gain, Rx data format, Rx overspeed on phone
line:
Bit 2-0 - Rx Gain, 000 (-10.5dB) through to 111 (0dB)
in 1.5dB steps
Bit 5-3 - Rx Data/Parity bits:
000 (5 data, no parity),
001 (5 data, parity),
010 (6 data, no parity),
011 (6 data, parity),
100 (7 data, no parity),
101 (7 data, parity),
110 (8 data, no parity) - default,
111 (8 data, parity)
Bit 7-6 - Rx USART overspeed mode:
00 (start/stop mode 2.3% overspeed) - default,
01 (start/stop mode 1.0% overspeed),
10 (start/stop mode no overspeed),
11 (Synchronous mode)
30
2004 CML Microsystems Plc
28
Default
D/866/4
V.22 bis Modem with AT Commands
CMX866
S-Register
Description
Reg
Range
Units
S27
0-255
Hex
Communications Protocol:
Bit 3-0 - Reserved
Bit 7-4 - Communications standard:
0000 (ATB0) Selects ITU-T V.22bis at
2400bps QAM,
0001 (ATB1) Selects ITU-T V.22 at 1200bps DPSK,
0010 (ATB2) Selects ITU-T V.23 with
Tx 75bps and Rx 1200bps FSK,
0011 (ATB3) Selects ITU-T V.23 with
Tx 1200bps and Rx 75bps FSK,
0100 (ATB4) No function. Reserved for future use,
0101 (ATB5) Selects ITU-T V.21 at 300bps FSK,
0110 (ATB6) Selects Bell 212A at 1200bps DPSK,
0111 (ATB7) Selects Bell 202 with
Tx 150bps and Rx 1200bps FSK,
1000 (ATB8) Selects Bell 202 with
Tx 1200bps and Rx 150bps FSK,
1001 (ATB9) Selects Bell 103 at 300bps FSK
Default
00
S28
0-255
1s
RTSN Timeout - The timeout for validation of a change
on the RTSN pin before it is actioned by returning to
Command mode from Data Transfer mode. (0 = timeout
disabled).
0
S29
0-255
10ms
Timed Break Recall Period - Sets the length of time
that the CMX866 breaks the line before reconnecting it
and continuing to dial the directory number.
30
1.5.4.6 Result Codes
Numeric Response (Decimal)
00
01
02
03
04
05
06
07
08
09
10
11
12
13
14
15
2004 CML Microsystems Plc
Word 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
29
(Not Yet Implemented)
D/866/4
V.22 bis Modem with AT Commands
1.5.5
CMX866
Tx USART
A flexible Tx USART is provided for all CMX866 modes. It can be programmed to transmit continuous
patterns, Start-Stop characters or Synchronous Data.
In both Synchronous Data and Start-Stop modes the data to be transmitted is written by the on-chip
µController into the 8-bit DSP Tx Data Register from which it is transferred to the Tx Data Buffer.
If Synchronous Data mode has been selected the 8 data bits in the Tx Data Buffer are transmitted serially
in the order in which they are received, ie. b0 being sent first.
In Start-Stop mode a single Start bit is transmitted, followed by 5, 6, 7 or 8 data bits from the Tx Data
Buffer - b0 first - followed by an optional Parity bit then - normally - one or two Stop bits. The Start, Parity
and Stop bits are generated by the USART as determined by the Tx Mode Register settings and are not
taken from the DSP Tx Data Register.
Figure 6a Tx USART
Every time the contents of the DSP Tx Data Register are transferred to the Tx Data Buffer, the Tx Data
Ready flag bit of the DSP Status Register is set to 1 to indicate that a new value should be loaded into
the DSP Tx Data Register. This flag bit is cleared to 0 when a new value is loaded into the DSP Tx Data
Register. The interpretation of this flag is handled automatically by the on-chip µController.
Figure 6b Tx USART Function (Start-Stop mode, 8 Data Bits + Parity)
If a new value is not loaded into the DSP Tx Data Register in time for the next DSP Tx Data Register to
Tx Data Buffer transfer then the DSP Status Register Tx Data Underflow bit will be set to 1. In this event
the contents of the Tx Data Buffer will be re-transmitted if Synchronous Data mode has been selected, or
if Start-Stop mode was selected then a continuous Stop signal (1) will be transmitted until a new value is
loaded into the DSP Tx Data Register.
In all modes the transmitted bit and baud rates are the nominal rates for the selected modem type, with
an accuracy determined by the XTAL frequency accuracy. Underspeed transmission is automatically
handled by the CMX866 in Start-Stop mode as it inserts extra Stop bit(s) if it has to wait for new data to
be loaded into the DSP Tx Data Register.
2004 CML Microsystems Plc
30
D/866/4
V.22 bis Modem with AT Commands
CMX866
The optional V.22/V.22 bis compatible data scrambler is enabled in V.22 and V.22bis handshake and
data transfer modes. Its function is to invert the next input bit in the event of 64 consecutive ones
appearing at its input. The scrambler uses the generating polynomial:
1 + x-14 + x-17
1.5.6
FSK and QAM/DPSK Modulators
Serial data from the USART is fed via the optional scrambler to the FSK modulator if V.21, V.23, Bell 103
or Bell 202 mode has been selected or to the QAM/DPSK modulator for V.22, V.22 bis and Bell 212A
modes.
The FSK modulator generates one of two frequencies according to the transmit mode and the value of
current transmit data bit.
The QAM/DPSK modulator generates a carrier of 1200Hz (Low Band, Calling modem) or 2400Hz (High
Band, Answering modem) which is modulated at 600 symbols/sec as described below:
For V.22 and Bell 212A 1200bps DPSK the transmit data stream is divided into groups of two
consecutive bits (dibits) which are encoded as a carrier phase change:
Dibit
(left-hand bit is the
first of the pair)
00
01
11
10
2004 CML Microsystems Plc
Phase change
+90°
0°
+270°
+180°
31
D/866/4
V.22 bis Modem with AT Commands
CMX866
For V.22 bis 2400bps QAM the transmit data stream is divided into groups of 4 consecutive data
bits. The first two bits of each group are encoded as a phase quadrant change and the last two
bits define one of four elements within a quadrant:
First two bits of group
(left-hand bit is the
first of the pair)
00
01
11
10
Phase quadrant change
+90° (e.g. quadrant 1 to 2)
0° (no change of quadrant)
+270° (e.g. quadrant 1 to 4)
+180° (e.g. quadrant 1 to 3)
Figure 7 V.22 bis Signal Constellation
1.5.7
Tx Filter and Equaliser
The FSK or QAM/DPSK modulator output signal is fed through the Transmit Filter and Equaliser block
which limits the out-of-band signal energy to acceptable limits. In 1200 and 2400 bps FSK, DPSK and
QAM modes this block includes a fixed compromise line equaliser which is automatically set for the
particular modulation type and frequency band being employed. This fixed compromise line equaliser
may be enabled or disabled by bit 1 of the S24 register. The amount of Tx equalisation provided
compensates for one quarter of the relative amplitude and delay distortion of ETS Test Line 1 over the
frequency band used.
1.5.8
DTMF/Tone Generator
In DTMF/Tones mode this block generates DTMF signals or single or dual frequency tones. In
QAM/DPSK modem modes it is used to generate the optional 550 or 1800Hz guard tone (see &Gn
command and S23 register).
1.5.9
Tx Level Control and Output Buffer
The outputs (if present) of the Transmit Filter and DTMF/Tone Generator are summed then passed
through the programmable Tx Level Control and Tx Output Buffer to the pins TXA and TXAN. The Tx
Output Buffer has symmetrical outputs to provide sufficient line voltage swing at low values of VDD and to
reduce harmonic distortion of the signal. The output level is adjusted by bits 0-2 of the S25 register.
2004 CML Microsystems Plc
32
D/866/4
V.22 bis Modem with AT Commands
CMX866
1.5.10 Rx DTMF/Tones Detectors
In Rx Tones Detect mode the received signal, after passing through the Rx Gain Control block, is fed to
the DTMF / Tones / Call Progress / Answer Tone detectors. The selection of the four separate detectors
is handled automatically by the on-chip µController:
The DTMF detector detects standard DTMF signals. A valid DTMF signal will set bit 5 of the DSP Status
Register to 1 for as long as the signal is detected. The output of this detector is not currently used by the
on-chip µController, however, this register can be accessed by the @R command.
The programmable tone pair detector includes two separate tone detectors. The first detector will set bit
6 of the DSP Status Register for as long as a valid signal is detected, the second detector sets bit 7, and
bit 10 of the DSP Status Register will be set when both tones are detected. By default, this
programmable tone pair detector is set to detect the dual alert tone pair (2130Hz and 2750Hz) used on
some Type 1 CLI systems. The output of this detector is not currently used by the on-chip µController,
however, this register can be accessed by the @R command.
The Call Progress detector measures the amplitude of the signal at the output of a 275 - 665 Hz
bandpass filter and sets bit 10 of the DSP Status Register to 1 when the signal level exceeds the
measurement threshold. This is handled automatically by the on-chip µController. When the CMX866 is
on-hook, the Call Progress detector can be enabled so that it will detect voice activity arising from a
parallel phone connection which is off-hook. The output of the DSP Status Register will need to be
monitored by the external host µC, using an @R command, for several seconds and decision taken on
whether there is voice activity.
10
0
-10
-20
dB
-30
-40
-50
-60
0
0.5
1
1.5
2
kHz
2.5
3
3.5
4
Figure 8a Response of Call Progress Filter
The Answer Tone detector measures both amplitude and frequency of the received signal and sets bit 6
or bit 7 of the DSP Status Register respectively when a valid 2225Hz or 2100Hz signal is received. This
is handled automatically by the on-chip µController, which looks for either of the Answer Tones.
2004 CML Microsystems Plc
33
D/866/4
V.22 bis Modem with AT Commands
CMX866
1.5.11 Rx Modem Filterering and Demodulation
When the receive part of the CMX866 is operating as a modem, the received signal is fed to a bandpass
filter to attenuate unwanted signals and to provide fixed compromise line equalisation for 1200 and 2400
bps FSK, DPSK and QAM modes. The characteristics of the bandpass filter and equaliser are determined
by the chosen receive modem type and frequency band. The fixed compromise line equaliser may be
enabled or disabled by bit 1 of the S24 register and compensates for one quarter of the relative amplitude
and delay distortion of ETS Test Line 1.
The responses of these filters, including the line equaliser and the effect of external components used in
Figures 4a and 4b, are shown in Figures 8b-e:
dB
10
10
0
0
-10
-10
-20
-20
-30
dB
-30
-40
-40
-50
-50
-60
-60
0
0.5
1
1.5
2
2.5
3
3.5
4
0
0.5
1
1.5
kHz
Figure 8b QAM/DPSK Rx Filters
dB
2
2.5
3
3.5
4
kHz
Figure 8c V.21 Rx Filters
10
10
0
0
-10
-10
-20
-20
-30
dB
-30
-40
-40
-50
-50
-60
-60
0
0.5
1
1.5
2
2.5
3
3.5
4
0
kHz
0.5
1
1.5
2
2.5
3
3.5
4
kHz
Figure 8d Bell 103 Rx Filters
Figure 8e V.23/Bell 202 Rx Filters
The signal level at the output of the Receive Modem Filter and Equaliser is measured in the Modem
Energy Detector block, compared to a threshold value, and the result is automatically handled by the onchip µController.
The output of the Receive Modem Filter and Equaliser is also applied to the FSK or QAM/DPSK
demodulator depending on the selected modem type.
The FSK demodulator recognises individual frequencies as representing received ‘1’ or ‘0’ data bits:
2004 CML Microsystems Plc
34
D/866/4
V.22 bis Modem with AT Commands
CMX866
The QAM/DPSK demodulator decodes QAM or DPSK modulation of a 1200Hz or 2400Hz carrier and is
used for V.22, V.22 bis and Bell 212A modes. It includes an adaptive receive signal equaliser (autoequaliser) that will automatically compensate for a wide range of line conditions in both QAM and DPSK
modes. It must be enabled when receiving 2400bps QAM by setting bit 2 of the S24 register. The autoequaliser can provide a useful improvement in performance in 1200bps DPSK as well as 2400bps QAM
modes, so although it must be disabled at the start of a handshake sequence, it can be enabled as soon
as scrambled 1200bps 1s have been detected.
Both FSK and QAM/DPSK demodulators produce a serial data bit stream which is fed to the Rx pattern
detector, descrambler and USART block (see Figure 9a). In QAM/DPSK modes the demodulator input is
also monitored for the V.22 bis handshake ‘S1’ signal.
The QAM/DPSK demodulator also estimates the received bit error rate by comparing the actual received
signal against an ideal waveform. This estimate is placed in bits 2-0 of the DSP Status Register.
However, the estimate is not required for CMX866 operation and so is ignored by the on-chip µController.
1.5.12 Rx Modem Pattern Detectors and Descrambler
See Figure 9a.
The 1010.. pattern detector operates only in FSK modes and will set bit 9 of the DSP Status Register
when 32 bits of alternating 1’s and 0’s have been received.
The ‘Continuous Unscrambled 1’s’ detector operates in all modem modes and will set bits 8 and 7 of the
DSP Status Register to 01 when 32 consecutive 1’s have been received.
The descrambler operates only in DPSK/QAM modes and is enabled automatically by the on-chip
µController.
The ‘Continuous Scrambled 1’s’ detector operates only in DPSK/QAM modes when the descrambler is
enabled and will set bits 8 and 7 of the DSP Status Register to 11 when 32 consecutive 1’s appear at the
output of the descrambler. To avoid possible ambiguity, the ‘Scrambled 1’s’ detector is disabled when
continuous unscrambled 1’s are detected.
The ‘Continuous 0’s’ detector will set bits 8 and 7 of the DSP Status Register to 10 when NX consecutive
0’s have been received, NX being 32 except when DPSK/QAM Start-Stop mode has been selected, in
which case NX = 2N + 4 where N is the number of bits per character including the Start, Stop and any
Parity bits.
All of these pattern detectors will hold the ‘detect’ output for 12 bit times after the end of the detected
pattern unless the received bit rate or operating mode is changed, in which case the detectors are reset
within 2ms.
The DSP Status Register is automatically polled by the on-chip µController, which then interprets the
results of these pattern detectors.
1.5.13 Rx Data Register and USART
A flexible Rx USART is provided for all modem modes. It can be programmed by bits 6 and 7 of the S26
register to treat the received data bit stream as Synchronous data or as Start-Stop characters.
In Synchronous mode the received data bits are all sent to the Rx Data Buffer, which is copied into the
DSP Rx Data Register after every 8 bits.
In Start-Stop mode the USART Control logic looks for the start of each character, then sends only the
required number of data bits (not parity) to the Rx Data Buffer. The parity bit (if used) and the presence
2004 CML Microsystems Plc
35
D/866/4
V.22 bis Modem with AT Commands
CMX866
of a Stop bit are then checked and the data bits in the Rx Data Buffer copied into the DSP Rx Data
Register.
Figure 9a Rx Modem Data Paths
Whenever a new character is copied into the DSP Rx Data Register, the Rx Data Ready flag bit of the
DSP Status Register is set to 1 to prompt the on-chip µController to read the new data and, in Start-Stop
mode, the Even Rx Parity flag bit of the DSP Status Register is updated.
In Start-Stop mode, if the Stop bit is missing (received as a 0 instead of a 1) the received character will
still be placed into the DSP Rx Data Register and the Rx Data Ready flag bit set, but the DSP Status
Register Rx Framing Error bit will also be set to 1 and the USART will re-synchronise onto the next 1 – 0
(Stop – Start) transition. The Rx Framing Error bit will remain set until the next character has been
received.
Figure 9b Rx USART Function (Start-Stop mode, 8 Data Bits + Parity)
If, for any reason, the on-chip µController has not read the previous data from the DSP Rx Data Register
by the time that new data is copied to it from the Rx Data Buffer, then the Rx Data Overflow flag bit of
the DSP Status Register will be set to 1.
The Rx Data Ready flag and Rx Data Overflow bits are automatically cleared to 0 when the DSP Rx Data
Register is read by the on-chip µController. The handling of these low-level status flags is performed
automatically by the on-chip µController and is transparent to the user.
2004 CML Microsystems Plc
36
D/866/4
V.22 bis Modem with AT Commands
1.6
Application Notes
1.6.1
Hardware Interface
CMX866
The CMX866 can be interfaced to an external host µC, as shown in Figure 11, or to an RS232 computer
port (via a level shifter IC, to generate ±6V), as shown in Figure 12. These are complete phone line
interface circuits for operation at VDD = 5.0V. Figure 12 includes the additional gyrator components which
may be required for CTR21 compliance.
It is recommended that the full, 9-wire interface should be used, where practical. This is illustrated
functionally in Figure 10a. In some applications it will be necessary to move the safety barrier to the
serial port interface of the CMX866. If opto-couplers are used to achieve the safety isolation required, a
reduced RS232 interface, shown in Figure 10b, may be preferred for economic reasons.
Figure 10a Full RS232 Link
Figure 10b Reduced RS232 Link
The TXD signal can be used to wake up the CMX866 from Powersave or 'Zero-Power' states, as shown
above. The external host µC should ignore CTSN and write a character byte to the CMX866 via the TXD
pin, which is connected to the DTRN pin. This will wake up the CMX866 because the DTRN pin is pulled
low. The byte written, and any further activity on the TXD pin for up to 30ms when coming out of 'ZeroPower' state (or up to 10µs when coming out of Powersave state), will be corrupted. Normal data transfer
can commence when the CTSN pin goes low, providing the RTSN pin is already low.
If the DTRN pin is not connected to the TXD pin, the TXD signal cannot be used on its own to wake up
the CMX866. If the DTRN pin is permanently wired low it will not be possible to wake up the CMX866
from an external host µC. Moreover, it will not be possible to put the CMX866 into either a Powersave or
'Zero-Power' state in the first place, so the device will remain permanently operational.
2004 CML Microsystems Plc
37
D/866/4
V.22 bis Modem with AT Commands
CMX866
Figure 11 Host µC Example (FCC68)
2004 CML Microsystems Plc
38
D/866/4
V.22 bis Modem with AT Commands
CMX866
Figure 12 RS232 Level Converter Example (CTR21)
2004 CML Microsystems Plc
39
D/866/4
V.22 bis Modem with AT Commands
CMX866
Figures 11 and 12 - Component List:
Reference
Value
Tolerance
Supplier
C1, C2
22pF
±20%
Generic
C3, C4, C6
100nF
±20%
Generic
C5, C7
10µF
±20%
Generic
C8
100nF
±20%
Generic
C9 (FCC)
not fitted
C9 (CTR21)
2.2µF, 16V
C10 (FCC)
33nF
±20%
Generic
C10 (CTR21)
100nF
±20%
Generic
C11
100pF
±20%
Generic
C12 (FCC)
not used
C12 (CTR21)
10µF, 50V
±20%
Generic
C13
100nF
±20%
Generic
C14
330nF, 250V
±20%
Syfer 1812J250
C15
330nF
±20%
Generic
C16 (FCC)
47pF
±10%
Generic
C16 (CTR21)
220pF
±10%
Generic
C17
100nF
±10%
Generic
D1, D2, D3, D4
not used
D1, D2, D3, D4
CBRHD-02
~
CENTRAL SEMI
D5
LCA110S
~
CLARE
D6
PS2701-1
~
NEC
D7
BAS16
~
Generic
F1
C515-1.25
~
BUSSMANN
Q1, Q2 (FCC)
not used
Q1, Q2 (CTR21)
FZT605
~
ZETEX
Q3 (FCC)
not used
Q3 (CTR21)
BC846ALT1
~
MOTOROLA
R1
100k
±5%
Generic
R2
100k
±5%
Generic
R3
620
±5%
Generic
R4 (FCC)
not used
R4 (CTR21)
33k
±5%
Generic
R5 (FCC)
not used
R5 (CTR21)
11.5 ,
125mW
±1%
Generic
R6
10k , 0.5W
±5%
Generic
R7, R8
not used
R9
120k
±1%
Generic
R10
180k
±1%
Generic
2004 CML Microsystems Plc
Comment
user selectable
replace with wire link
±20%
Generic
non-polarised
polarised, electrolytic
(FCC)
40
(CTR21)
also use a BAS16 diode
1.25A slow blow
user selectable
D/866/4
V.22 bis Modem with AT Commands
Reference
CMX866
Value
Tolerance
Supplier
Comment
R11 (FCC)
62k
±1%
Generic
optimum value =
64k9
R11 (CTR21)
56k
±1%
Generic
optimum value =
57k6
R12
100k
±1%
Generic
R13
390
±1%
Generic
optimum value = 392
R14
5k6
±1%
Generic
optimum value =
6k04
R15
not used
R16
470k
±5%
Generic
R17
20k
±5%
Generic
T1 (FCC)
82111
~
MIDCOM
T1 (CTR21)
82107
~
MIDCOM
X1
11.0592MHz
±0.01%
RALTRON
Z1 (FCC)
not used
Z1 (CTR21)
P6SMB33CAT
3
~
MOTOROLA
Z2
CMPZDA4V3
~
CENTRAL SEMI
Z3
CMPZDA18V
~
CENTRAL SEMI
Z4
P3100SC
~
TECCOR
310V SIDACTOR
MAX3241
MAX3241
~
MAXIM
LEVEL CONVERTER
CMX866
CMX866
~
CML
MODEM IC
2004 CML Microsystems Plc
41
D/866/4
V.22 bis Modem with AT Commands
1.6.2
CMX866
Calling Modem AT Commands
General Commands for Initialisation
• wake-up CMX866 from 'Zero-Power' state
• restore factory defaults
• set Tx gain and data format
• set communications standard
• set Rx gain and data format
• set guard time (if required)
• set lost carrier to hang-up delay
• set other features (as required)
(pull DTRN pin low)
ATZ
ATS25=x
ATS27=x
or
ATBn
ATS26=x
ATS23=x
or
AT&Gn
ATS10=x
(S12, S14, S24, S28 and S29 registers)
Specific Tx Commands
• set calling and response characteristics
• set DTMF tone duration
• set pause time for comma dial modifier
• set wait for carrier after dial
• set wait time for blind dialling
• check correct settings
ATS22=x
ATS11=x
ATS8=x
ATS7=x
ATS6=x
AT&V
or
ATXn
Call Setup
• go off-hook and dial directory number
ATD<number>
• progress call and go to data mode when call established.
(This is automatic)
• return to command mode
<escape sequence>
• go on-hook
ATH0
• return CMX866 to 'Zero-Power' state
AT&Z0
1.6.3
Answering Modem AT Commands
General Commands for Initialisation
• wake-up CMX866 from 'Zero-Power' state
• set features (as required)
(pull DTRN pin low)
(see above)
Specific Rx Commands
• set handshake timeout
• enable automatic answer
• check correct settings
ATS17=x
ATS0=x
AT&V
Call Answer
• go off-hook and answer an incoming call on RING
ATA
• progress call and go to data mode when call established.
(This is automatic)
• return to command mode
<escape sequence>
• go on-hook
ATH0
• return CMX866 to 'Zero-Power' state
AT&Z0
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1.6.4
CMX866
RS232 Transaction Sequence
A typical RS232 transaction sequence is shown in Figure 13 below:
Figure 13 RS232 Transaction Sequence
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1.7
Performance Specification
1.7.1
Electrical Performance
CMX866
1.7.1.1 Absolute Maximum Ratings
Exceeding these maximum ratings can result in damage to the device.
Min.
-0.3
-0.3
-50
Supply (VDD - VSS)
Voltage on any pin to VSS
Current into or out of VDD and VSS pins
Current into RDRVN pin (RDRVN pin low)
Current into or out of any other pin
-20
D1 Package
Total Allowable Power Dissipation at Tamb = 25°C
... Derating
Storage Temperature
Operating Temperature
Min.
D6 Package
Total Allowable Power Dissipation at Tamb = 25°C
... Derating
Storage Temperature
Operating Temperature
Min.
-55
-40
-55
-40
Max.
7.0
VDD + 0.3
+50
+50
+20
Units
V
V
mA
mA
mA
Max.
1000
13
+125
+85
Units
mW
mW/°C
°C
°C
Max.
550
9.0
+125
+85
Units
mW
mW/°C
°C
°C
Max.
5.5
+85
Units
V
°C
1.7.1.2 Operating Limits
Correct operation of the device outside these limits is not implied.
Notes
Supply (VDD - VSS)
Operating Temperature
2004 CML Microsystems Plc
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Min.
2.7
-40
D/866/4
V.22 bis Modem with AT Commands
CMX866
1.7.1.3 Operating Characteristics
For the following conditions unless otherwise specified:
VDD = 2.7V to 5.5V at Tamb = -40 to +85°C,
Xtal Frequency = 11.0592MHz ± 0.01% (100ppm)
0dBm corresponds to 775mVrms.
DC Parameters
IDD
('Zero-Power' mode)
IDD
(Powersave mode, VDD = 3.0V)
IDD
(Powersave mode, VDD = 5.0V)
IDD
(µC operating, DSP powerdown,
VDD = 3.0V)
IDD
(µC operating, DSP powerdown,
VDD = 5.0V)
IDD
(µC and DSP operating, VDD = 3.0V)
IDD
(µC and DSP operating, VDD = 5.0V)
IDD
(µC and DSP operating, VDD = 3.0V)
IDD
(µC and DSP operating, VDD = 5.0V)
Logic '1' Input Level
Logic '0' Input Level
Logic Input Leakage Current (Vin = 0 to VDD),
(excluding XTAL/CLOCK input)
Output Logic '1' Level (lOH = 2 mA)
Output Logic '0' Level (lOL = -3 mA)
IRQN O/P 'Off' State Current (Vout = VDD)
RD and RT pin Schmitt trigger input high-going
threshold (Vthi) (see Figure 14)
RD and RT pin Schmitt trigger input low-going
threshold (Vtlo) (see Figure 14)
RDRVN ‘ON’ resistance to VSS (VDD= 3.0V)
RDRVN ‘OFF’ resistance to VDD (VDD= 3.0V)
Notes
1, 2
1, 2
1, 2
1
Min.
-
Typ.
3.0
0.6
1.5
1.7
Max.
10.0
1.5
3.0
3.5
Units
µA
mA
mA
mA
1
-
3.7
7.5
mA
1, 3
1, 3
1
1
4
4
70%
-1.0
3.4
6.2
5.0
9.0
-
7.0
12.5
10.0
18.0
30%
+1.0
mA
mA
mA
mA
VDD
VDD
µA
80%
0.56VDD
-
VDD
V
µA
V
0.44VDD
- 0.6V
-
-
0.4
1.0
0.56VDD
+ 0.6V
0.44VDD
50
1300
70
3000
Ω
Ω
XTAL/CLOCK Input
(timings for an external clock input)
'High' Pulse Width
'Low' Pulse Width
Notes
Min.
Typ.
Max.
Units
30
30
-
-
ns
ns
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CMX866
Transmit QAM and DPSK Modes
(V.22, Bell 212A, V.22 bis)
Carrier frequency, high band
Carrier frequency, low band
Baud rate
Bit rate (V.22, Bell 212A)
Bit rate (V.22 bis)
550Hz guard tone frequency
550Hz guard tone level wrt data signal
1800Hz guard tone frequency
1800Hz guard tone level wrt data signal
Notes
Min.
Typ.
Max.
Units
5
5
6
6
6
548
-4.0
1797
-7.0
2400
1200
600
1200
2400
550
-3.0
1800
-6.0
552
-2.0
1803
-5.0
Hz
Hz
Baud
bps
bps
Hz
dB
Hz
dB
Transmit V.21 FSK Mode
Baud rate
Mark (logical 1) frequency, high band
Space (logical 0) frequency, high band
Mark (logical 1) frequency, low band
Space (logical 0) frequency, low band
Notes
6
Min.
1647
1847
978
1178
Typ.
300
1650
1850
980
1180
Max.
1653
1853
982
1182
Units
Baud
Hz
Hz
Hz
Hz
Transmit Bell 103 FSK Mode
Baud rate
Mark (logical 1) frequency, high band
Space (logical 0) frequency, high band
Mark (logical 1) frequency, low band
Space (logical 0) frequency, low band
Notes
6
Min.
2222
2022
1268
1068
Typ.
300
2225
2025
1270
1070
Max.
2228
2028
1272
1072
Units
Baud
Hz
Hz
Hz
Hz
Transmit V.23 FSK Mode
Baud rate
Mark (logical 1) frequency, 1200 baud
Space (logical 0) frequency, 1200 baud
Mark (logical 1) frequency, 75 baud
Space (logical 0) frequency, 75 baud
Notes
6
Min.
1298
2097
389
449
Typ.
1200/75
1300
2100
390
450
Max.
1302
2103
391
451
Units
Baud
Hz
Hz
Hz
Hz
Transmit Bell 202 FSK Mode
Baud rate
Mark (logical 1) frequency, 1200 baud
Space (logical 0) frequency, 1200 baud
Mark (logical 1) frequency, 150 baud
Space (logical 0) frequency, 150 baud
Notes
6
Min.
1198
2197
386
486
Typ.
1200/150
1200
2200
387
487
Max.
1202
2203
388
488
Units
Baud
Hz
Hz
Hz
Hz
DTMF/Single Tone Transmit
Tone frequency accuracy
Distortion
Notes
7
Min.
-0.2
-
Typ.
1.0
Max.
+0.2
2.0
Units
%
%
Transmit Output Level
Modem and Single Tone modes
DTMF mode, Low Group tones
DTMF: level of High Group tones wrt Low Group
Tx output buffer gain control accuracy
Notes
7
7
7
7
Min.
-4.0
-2.0
+1.0
-0.25
Max.
-2.0
0.0
+3.0
+0.25
Units
dBm
dBm
dB
dB
2004 CML Microsystems Plc
46
Typ.
-3.0
-1.0
+2.0
-
D/866/4
V.22 bis Modem with AT Commands
CMX866
Receive QAM and DPSK Modes
(V.22, Bell 212A, V.22 bis)
Carrier frequency (high band)
Carrier frequency (low band)
Baud rate
Bit rate (V.22, Bell 212A)
Bit rate (V.22 bis)
Notes
Min.
Typ.
Max.
Units
9
9
9
2392
1192
-
2400
1200
600
1200
2400
2408
1208
-
Hz
Hz
Baud
bps
bps
Receive V.21 FSK Mode
Acceptable baud rate
Mark (logical 1) frequency, high band
Space (logical 0) frequency, high band
Mark (logical 1) frequency, low band
Space (logical 0) frequency, low band
Notes
Min.
297
1638
1838
968
1168
Typ.
300
1650
1850
980
1180
Max.
303
1662
1862
992
1192
Units
Baud
Hz
Hz
Hz
Hz
Receive Bell 103 FSK Mode
Acceptable baud rate
Mark (logical 1) frequency, high band
Space (logical 0) frequency, high band
Mark (logical 1) frequency, low band
Space (logical 0) frequency, low band
Notes
Min.
297
2213
2013
1258
1058
Typ.
300
2225
2025
1270
1070
Max.
303
2237
2037
1282
1082
Units
Baud
Hz
Hz
Hz
Hz
Receive V.23 FSK Mode
1200 baud
Acceptable baud rate
Mark (logical 1) frequency
Space (logical 0) frequency
75 baud
Acceptable baud rate
Mark (logical 1) frequency
Space (logical 0) frequency
Notes
16
Min.
Typ.
Max.
Units
1188
1280
2080
1200
1300
2100
1212
1320
2120
Baud
Hz
Hz
74
382
442
75
390
450
76
398
458
Baud
Hz
Hz
Receive Bell 202 FSK Mode
1200 baud
Acceptable baud rate
Mark (logical 1) frequency
Space (logical 0) frequency
150 baud
Acceptable baud rate
Mark (logical 1) frequency
Space (logical 0) frequency
Notes
16
Min.
Typ.
Max.
Units
1188
1180
2180
1200
1200
2200
1212
1220
2220
Baud
Hz
Hz
148
377
477
150
387
487
152
397
497
Baud
Hz
Hz
Rx Modem Signal
(FSK, DPSK and QAM Modes)
Signal level
Signal to Noise Ratio (noise flat 300-3400Hz)
Notes
Min.
Typ.
Max.
Units
10
-45
20
-
-9
-
dBm
dB
2004 CML Microsystems Plc
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16
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CMX866
Rx Modem S1 Pattern Detector
(DPSK and QAM modes)
Will detect S1 pattern lasting for
Will not detect S1 pattern lasting for
Hold time (minimum detector ‘On’ time)
Notes
Min.
Typ.
Max.
Units
90.0
-
ms
5.0
-
72.0
-
Rx Modem Energy Detector
Detect threshold (‘Off’ to ‘On)
Undetect threshold (‘On’ to ‘Off’)
Hysteresis
Detect (‘Off’ to ‘On’) response time
QAM and DPSK modes
300 and 1200 baud FSK modes
150 and 75 baud FSK modes
Undetect (‘On’ to ‘Off’) response time
QAM and DPSK modes
300 and 1200 baud FSK modes
150 and 75 baud FSK modes
Notes
10,11
10,11
10,11
Min.
-48.0
2.0
Typ.
-
Max.
-43.0
-
Units
dBm
dBm
dB
10,11
10,11
10,11
10.0
8.0
16.0
-
35.0
30.0
60.0
ms
ms
ms
10,11
10,11
10,11
10.0
10.0
20.0
-
55.0
40.0
80.0
ms
ms
ms
Rx Answer Tone Detectors
Detect threshold (‘Off’ to ‘On)
Undetect threshold (‘On’ to ‘Off’)
Hysteresis
Detect (‘Off’ to ‘On’) response time
Undetect (‘On’ to ‘Off’) response time
2100Hz detector
‘Will detect’ frequency
‘Will not detect’ frequency
2225Hz detector
‘Will detect’ frequency
‘Will not detect’ frequency
Notes
10,12
10,12
10,12
10,12
10,12
Min.
-48.0
2.0
30.0
7.0
Typ.
33.0
18.0
Max.
-43.0
45.0
25.0
Units
dBm
dBm
dB
ms
ms
2050
-
-
2160
2000
Hz
Hz
2160
2335
-
2285
-
Hz
Hz
Rx Call Progress Energy Detector
Bandwidth (-3dB points) See Figure 8a
Detect threshold (‘Off’ to ‘On)
Undetect threshold (‘On’ to ‘Off’)
Detect (‘Off’ to ‘On’) response time
Undetect (‘On’ to ‘Off’) response time
Notes
Min.
275
-42.0
30.0
6.0
Typ.
36.0
8.0
Max.
665
-37.0
45.0
50.0
Units
Hz
dBm
dBm
ms
ms
Receive Input Amplifier
Input impedance (at 100Hz)
Notes
Min.
10.0
Typ.
Max.
Units
Moh
m
V/V
dB
10,13
10,13
10,13
10,13
Open loop gain (at 100Hz)
Rx Gain Control Block accuracy
2004 CML Microsystems Plc
10000
-0.25
48
+0.25
ms
D/866/4
V.22 bis Modem with AT Commands
CMX866
DTMF Decoder
Valid input signal levels
(each tone of composite signal)
Not decode level
(either tone of composite signal)
Twist = High Tone/Low Tone
Frequency Detect Bandwidth
Frequency Not Detect Bandwidth
Max level of low frequency noise (i.e dial tone)
Interfering signal frequency <= 550Hz
Interfering signal frequency <= 450Hz
Interfering signal frequency <= 200Hz
Max. noise level wrt. signal
DTMF detect response time
DTMF de-response time
Status Register b5 high time
‘Will Detect’ DTMF signal duration
‘Will Not Detect’ DTMF signal duration
Pause length detected
Pause length ignored
Notes:
Notes
Min.
Typ.
Max.
Unit
10
-30.0
-
0.0
dBm
10
-10.0
±1.8
-
-
-36.0
6.0
±3.5
dBm
dB
%
%
14
14
14
14,15
14.0
40.0
30.0
-
25.0
-
0.0
10.0
20.0
-10.0
40.0
30.0
15.0
dB
dB
dB
dB
ms
ms
ms
ms
ms
ms
ms
1. At 25°C, not including any current drawn from the CMX866 pins by external circuitry
other than X1, C1 and C2.
2. All logic inputs at VSS except for RT, DTRN and RTSN inputs which are at DVDD.
3. DSP is powered up but in a reset state.
4. Excluding RD and RT pins.
5. % carrier frequency accuracy is the same as XTAL/CLOCK % frequency accuracy.
6 Tx signal % baud or bit rate accuracy is the same as XTAL/CLOCK % frequency
accuracy.
7. Measured between TXA and TXAN pins with Tx Level Control gain set to 0dB, 1k2Ω load
between TXA and TXAN, at VDD = 3.0V (levels are proportional to VDD - see section
1.4.2). Level measurements for all modem modes are performed with random
transmitted data and without any guard tone. 0dBm = 775mVrms.
8. Measured on the 2 or 4-wire line using the line interface circuits described in section
1.4.2 with the Tx line signal level set to -10dBm for QAM, DPSK, FSK or single tones, 6dBm and -8dBm for DTMF tones. Excludes any distortion due to external components
such as the line coupling transformer.
9. These are the bit and baud rates of the line signal, the acceptable tolerance is ±0.01%.
10. Rx 2 or 4-wire line signal level assuming 1dB loss in line coupling transformer with Rx
Gain Control block set to 0dB and external components as section 1.4.2.
11. Thresholds and times measured with random data for QAM and DPSK modes,
continuous binary ‘1’ for all FSK modes. Fixed compromise line equaliser enabled.
Signal switched between off and -33dBm
12. ‘Typical’ value refers to 2100Hz or 2225Hz signal switched between off and -33dBm.
Times measured with respect to the received line signal
13. ‘Typical’ values refers to 400Hz signal switched between off and -33dBm
14. Referenced to DTMF tone of lower amplitude.
15. Flat Gaussian Noise in 300-3400Hz band.
16. For V.23r (Tx1200/Rx75) and Bell 202r (Tx1200/Rx150) the calling modem carrier detect
time is typically 1700ms.
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V.22 bis Modem with AT Commands
CMX866
3.5
3
2.5
2
Vin
1.5
1
Vthi
0.5
Vtlo
0
2.5
3
3.5
4
4.5
5
5.5
Vdd
Figure 14 Typical Schmitt Trigger Input Voltage Thresholds vs. VDD
0
-10
Bell 202
-20
-30
dBm
-40
-50
-60
-70
10
100
1000
10000
100000
Hz
Figure 15 Maximum Out of Band Tx Line Energy Limits (see note 8)
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1.7.2
CMX866
Packaging
Figure 16a 28-pin SOIC (D1) Mechanical Outline: Order as part no. CMX866D1
Figure 16b 28-pin SSOP (D6) Mechanical Outline: Order as part no. CMX866D6
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CMX866
Handling precautions: This product includes input protection, however, precautions should be taken to prevent device damage from electrostatic discharge. 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 this product specification. CML has a policy of testing
every product shipped using calibrated test equipment to ensure compliance with this product specification. Specific testing of all circuit
parameters is not necessarily performed.
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/
Oval Park, Langford, Maldon,
Essex,
CM9 6WG - England.
4800 Bethania Station Road,
Winston-Salem,
NC 27105 - USA.
No 2 Kallang Pudding Road,
#09 to 05/06 Mactech
Industrial Building,
Singapore 349307
No. 218, Tian Mu Road
West, Tower 1, Unit 1008,
Shanghai Kerry Everbright
City, Zhabei,
Shanghai 200070,
China.
Tel: +44 (0)1621 875500
Tel: +65 6745 0426
Fax: +44 (0)1621 875600
Tel: +1 336 744 5050,
800 638 5577
Fax: +1 336 744 5054
Fax: +65 6745 2917
Tel: +86 21 6317 4107
+86 21 6317 8916
Fax: +86 21 6317 0243
Sales:
[email protected]
Sales:
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Sales:
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Sales:
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Technical Support:
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Technical Support:
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Technical Support:
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Technical Support:
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