Siemens AC75 Manuel D’Utilisation

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AC75_ATC_V01.002

Page 28 of 569

10/30/06

Confidential / Released

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.