Nortel Networks 1000M - Manual (Page 469)

CRC protocol specifications 469
crc += (((c<<=1) & 0400)!= 0);
crc ^= 0x1021;
}
else {
crc <<= 1;
crc += (((c<<=1) & 0400)!= 0);
}
}
return crc;
A receiving program that wishes to receive in CRC mode implements the
mode setting handshake by sending a <C>. After the receiver has sent
the <C> it waits up to 3 seconds for the <soh> that starts the first block. If
no <soh> is received within 3 seconds, the receiver will re-send a <C>.
After the mode has been sent by the initial <C> the protocol follows the
flow shown in the following example.
Example
This flow example shows a case where the receiver requests transmission
in the CRC mode and the sender supports the CRC option. The example
includes various transmission errors. <xxxx> represents 2 CRC bytes.
SENDERRECEIVER
<---<C>
times out after 3.4 seconds,
<---<C>
times out after 3.4 seconds,
<---<C>
times out after 3.4 seconds,
<---<C>
times out after 3.4 seconds,
<---<C>
<soh> 01 FE -data- <xxxx>--->
<---<ack> <soh> 02 FD -data- <xxxx> --->(data gets line hit)
<---<nak>
<soh> 02 FD -data- <xxxx>--->
<---<ack>
<soh> 03 FC -data- <xxxx>--->
(ack gets garbage)<---<ack>
times out after 6.8 seconds
<---<nak>
<soh> 03 FC -data- <xxxx>--->
<---<ack>
<eot>--->
<---<ack>
Nortel Communication Server 1000
Communication Server 1000M and Meridian 1 Small System Installation and Commissioning
NN43011-310 01.04 Standard
Release 5.0 13 May 2008
Copyright © 2008, Nortel Networks
.