Cinterion
®
ENS22-E AT Command Set
1.5 Communication between Customer Application and
Cinterion
®
ENS22-E
ENS22-E_ATC_V01.000
19/02/11
Page 15 of 189
1.5
Communication between Customer Application and
Cinterion
®
ENS22-E
After power-up or restart ensure that the UE 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
Cinterion
®
ENS22-E's signal lines refer to the Hardware Interface Description
Leaving hardware flow control unconsidered the Customer Application (TE) is coupled with the
Cinterion
®
ENS22-E (UE) 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
Cinterion
®
ENS22-E 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
Cinterion
®
ENS22-E the opportunity to the transmission
of pending
URCs and get necessary service.
• The TE shall communicate with the
Cinterion
®
ENS22-E using activated echo (
1), i.e. the
Cinterion
®
ENS22-E echoes charac-ters 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
Cinterion
®
ENS22-E 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.