Siemens AC75 User Manual
Page 28
AC75 AT Command Set
1.7 Communication between Customer Application and AC75
s
AC75_ATC_V01.002
Page 28 of 569
10/30/06
Confidential / Released
1.7
Communication between Customer Application and AC75
Leaving hardware flow control unconsidered the Customer Application (TE) is coupled with the AC75 (ME) via a
receive and a transmit line.
Since both lines are driven by independent devices collisions may (and will) happen. For example, if the TE
issues an AT command the AC75 starts sending a URC. This will probably cause the TE to misinterpret of the
URC being part of the AT command's response.
To avoid this conflict the following measures must be taken:
• If an AT command is finished (with "OK" or "ERROR") the TE shall always wait at least 100 milliseconds
before sending the next one.
This gives the AC75 the opportunity to transmit pending URCs and get necessary service.
Note that some AT commands may require more delay after "OK" or "ERROR" response, refer to the following
command specifications for details.
• The TE shall communicate with the AC75 using activated echo (
1), i.e. the AC75 echoes characters
received from the TE.
Hence, when the TE receives the echo of the first character "A" of the AT command just sent by itself it has
control both over the receive and the transmit paths.