EV6240 Datasheet, PDF (34/47 Pages) CML Microcircuits – Opto-Isolated serial interface capability

Evaluation Kit for CMX624/CMX644A
EV6240
1.6.6 Additional Information
1.6.6.1 CMX624 Optional Connection Settings
The CMX624 data format can be modified by the user before a Modem mode connection is attempted.
This can be achieved using the AT@RE0=x command (where x is the decimal register setting).
At power up the CMX624 SETUP register defaults to 0 which corresponds to 8 bit data, no parity and
1 stop bit.
The Rx Equaliser and Tx level control bit settings are also optional and should be enabled if required
before a connection is attempted.
1.6.6.2 CMX644A Optional Connection Settings
The CMX644A Tx/Rx gain is controlled by the user. The settings in the GAIN BLOCKS register will
only be used during handshaking and data transfer if the Tx gain control bits (TG0-TG3) are not equal
to zero (o/p off). If a connection is attempted and the Tx gain control bits are zero the firmware will
modify the Tx gain control bits of the GAIN BLOCKS register to give a Tx gain of 0dB.
The Tx/Rx Equaliser control bit settings are also optional and should be enabled if required before a
connection is attempted.
1.6.6.3 V23/Bell 202 Handshaking Sequence for an EV6240 Calling Modem via a 2-Wire Line
Figure 8 is a flowchart illustrating the firmware handshaking sequence performed when an on-board
CMX624 modem originates a call to an external V23/Bell 202 simulator/modem.
The firmware assumes the external equipment has been configured to answer the call using the
appropriate protocol.
The states shown in the diagram are as follows:
Calling Modem Entry Point
On entry the Modem will be off-hook, DTMF dialling and the required call progress monitoring
completed.
State 1
Start the Wait for Carrier after Dial Timer (setting stored in S7).
Check Communications Standard selected by user (Bell or ITU-T).
If Bell
Goto State 4.
State 2
Set up CMX624 to detect 2100Hz Answer tone.
Start transmitting the 1300Hz calling tone (Cadence 0.6s on and 1.5s off).
If the 2100Hz Answer tone is detected then start Validation Timer (setting stored in S18).
If the 2100Hz Answer tone is detected for 1s stop transmitting the 1300Hz Calling tone then goto
State 3.
If the Wait for Carrier after Dial Timer expires then Hang Up and Exit.
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© 1999 Consumer Microcircuits Limited
UM6240/3