AT Command Set
MC35_ATC_01_V04.00 Page 40 of 238 02.04.2002
• Take into account that a delay of 100 ms is required between a response t o the
last command (e.g. OK) and the next command on the same line.
• When you enter AT+IPR=0, autobauding will be activated after the resp onse to
the last command is received.
• When local echo is active (ATE1) and you enter AT+IPR=x with oth er com-
mands you may encounter the following problem: If switching to the ne w bit
rate takes effect while a response is being transmitted, the last bytes m ay be
sent at the new bit rate and thus, not properly transmitted. The following com-
mands will be correctly sent at the new bit rate.
2.45.1 Autobauding
Autobauding allows the GSM engine to automatically detect the bitrate configured in th e host applica-
tion. The serial interface of the GSM engine supports autobaud ing for the following bitrates: 1200,
2400, 4800, 9600, 19200, 38400, 57600, 115200. Factory setting is autobauding enab led. This gives
you the flexibility to put the GSM engine into operation no matter what bitrate your host application is
configured to.
To take advantage of autobaud mode specific attention must be paid to the following requirements:
Synchronization between DTE and DCE
Ensure that DTE and DCE are correctly synchronized and the bitrate used by the DTE is detected by
the DCE (= ME). To allow the bitrate to be synchronized simply iss ue an "AT" or "at" string. This is
necessary
• after you have activated autobauding
• when you start up the GSM engine while autobauding is enabled. It is rec ommended to wait 3 to 5
seconds before sending the first AT character. Otherwise undefined char acters might be returned.
If you want to use autobauding and autoanswer at the same time, you can easily enable the synchro-
nization, when you activate autobauding first and then configure the au toanswer mode (ATS0=0).
Restrictions on autobauding operation
• The serial interface has to be operated at 8 data bits, no parity and 1 stop b it (factory setting).
• The A/ command (and a/) cannot be used.
• Only the strings “AT“ or “at“ can be detected (neither “aT“ nor “At“).
• The Unsolicited Result Codes "^SYSSTART", "^SYSSTART ALARM MODE" and "^SYSSTART
CHARGE-ONLY MODE" are not indicated when you start up the ME while au tobauding is enabled.
This is due to the fact that the new bitrate is not detected unless DTE and DCE are correctly syn-
chronized as described above.
• Any other Unsolicited Result Codes that may be issued before the ME detects the new bitrate (by
receiving the first AT command string) will be sent at the previous b itrate.
• It is not recommended to switch to autobauding from a bitrate that cannot be detected by the auto-
baud mechnism (e.g. 300 baud). Responses to +IPR=0 and any comm ands on the same line might
be corrupted.
• When entering several AT commands on the same line, consider the r equirements described in the
Notes of Chapter 2.45.
• See also AT+ILRR Set TE-TA local rate reporting , pg. 37
Autobauding and multiplex mode
If autobauding is active you cannot switch to multiplex mode (see +CMUX, pg. 91) . Vice versa, when
you run the multiplex mode, the write command AT+IPR=<rate> cannot be used.