CMX867D2 CML Microcircuits, CMX867D2 Datasheet - Page 35

• Manufacturer Part Number: CMX867D2
• Description: Low power V.22 modem
• Manufacturer: CML Microcircuits

Low Power V.22 Modem
1.6.2
This section describes how the CMX867 can be used in a V.22 Answering modem application, employing
V.25 automatic answering and the V.22 recommended handshake sequence. This attempts to establish a
1200 bps connection.
1.
2.
3.
4.
5.
6.
7.
8.
9.
2001 Consumer Microcircuits Limited
It is assumed that the CMX867 will be in Powersave mode, with the Ring Detector circuits
monitoring the line.
When a ring signal is detected connect the line (go off hook), set a 2150ms timer and power up the
CMX867, setting the Tx Mode Register to DTMF/Tones mode (set for ‘no tone’ at this time) and the
Rx Mode Register to V.22 1200bps Low Band receive, descrambler enabled, Rx USART disabled.
When the 2150ms timer expires set the Tx Mode Register to transmit the 2100Hz answer tone and
set a 3300ms timer.
When the 3300ms timer expires set the Tx Mode Register to no tone and set a 75ms timer.
When the 75ms timer expires set the Tx Mode Register for V.22 High Band 1200bps transmission of
unscrambled 1s. Monitor the received signal for scrambled 1s.
When scrambled 1s have been detected for 270ms, set the Tx Mode Register to V.22 High Band
1200bps scrambled 1s transmission and set a 765ms timer and enable the Rx USART.
Load the Tx Data Buffer with the first data to be transmitted.
When the 765ms timer expires set the Tx Mode Register for Start-Stop or Synchronous
transmission of data from the Tx Data Buffer. This will start transmission of the data loaded in step
7.
A 1200bps data connection has now been established.
V.22 Answering Modem Application
35
CMX867
D/867/2