Cinterion
®
EHS6 AT Command Set
1.6 Communication between Customer Application and EHS6
EHS6_ATC_V03.001
15/12/3
Confidential / Released
Page 21 of 513
1.6
Communication between Customer Application and EHS6
After power-up or restart ensure that the ME is in ready state before trying to send any AT command or data. For
detailed information on timing conditions, signal states and particularly the startup behavior of the EHS6's signal
lines refer to the Hardware Interface Description
.
Leaving hardware flow control unconsidered the Customer Application (TE) is coupled with the EHS6 (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 and the EHS6 starts sending a URC. This will probably cause the TE to misinterpret 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 ms before sending
the next one. This applies to bit rates of 9600 bps or higher (see
). At bit rates below 9600 bps the
delay must be longer: 300 ms at 1200 bps, and 500 ms at 300 bps.
The pause between two AT commands gives the EHS6 the opportunity to the transmission of pending URCs
and get necessary service.
• The TE shall communicate with the EHS6 using activated echo (
1), i.e. the EHS6 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.
Using Backspace at command line:
• As the standard GSM alphabet does not provide a backspace functionality the EHS6 is designed to use the
character "08" (hex 0x08) as backspace for command line input. This allows the user to easily erase the last
character when writing an AT command. On the other hand, this solution requires entering the escape
sequence \08 for writing the "ò" character in GSM character string parameters.
• If command echo is enabled (
1) Backspace may cause 08 - 32 - 08 (decimal) character sequence or no
echo, depending on serial interface and speed of character input.