User's Manual

Table Of Contents
AT+i Command Set
AT+i Programmer‘s Manual Version 8.32 1-4
In auto baud mode, iChip expects an A or a character. This is usually the first character
sent, since in command mode a meaningful command is always prefixed by AT+i.
The host may send an a or A to the iChip to allow it to determine the host‘s baud rate. It
may also send a complete AT+i command. In any case, iChip detects the A or a character,
determines the correct baud rate, and configures its serial channel during the stop bit.
Thus, the next character is received by the serial port at the correct baud rate. The A itself
is retained as well. iChip supports auto baud rate detection for the following baud rates:
2400, 4800, 9600, 19200, 38400, 57600, and 115200.
When the BDRF parameter contains a fixed baud rate, iChip initializes to the specified
baud rate without entering auto baud rate mode. Commands issued by the host must be
sent using that baud rate in order to be recognized. In this case, iChip can be forced into
auto baud rate mode by holding the special input signal low for not more than five
seconds following power-up.
iChip dial-up mode only: When the BDRM parameter is set to an a value, iChip
assumes the attached modem has the auto baud rate feature. Once the hostiChip baud
rate is determined, the iChipmodem baud rate is set to the same rate. Any other BDRM
value is used as a fixed baud rate to the modem.
1.8 High Speed USART
Very high baud rates, up to 3Mbps, can be reached between host and iChip via one of
iChip‘s USARTs. The BDRD parameter acts as baud rate divider. When set to ‗0‘, iChip
sets its host USART baud rate according to the value of the BDRF parameter. When set
to any value in the range 1-255, it divides the maximum supported baud rate 3Mbps
by that value. The quotient of this division is set as the host baud rate, and the value of
BDRF is ignored. For example, if BDRD is set to 2, then the host baud rate will be
3Mbps÷2=1.5Mbps.
If the iChipmodem interface is a USART, BDRD is set to any value other than ‗0‘, and
the modem baud rate is set to Auto (BDRM=‗a‘), then the modem baud rate will be set to
a fixed value of 115,200bps.
In SerialNET mode, you can specify that hostiChip baud rate over USART be
determined by the BDRD parameter. You do so by setting the first field of the SNSI
parameter (<baud>) to ‗0‘.
1.9 Reset via Serial Link
Issuing a BREAK signal on the host serial link effectively resets the iChip. A BREAK
signal is issued by transmitting a LOW (zero value) for a period that is longer than 23 bits
at the current baud rate. Considerably lowering the host baud rate (300 baud or less) and
transmitting a binary zero generates a BREAK signal. After a BREAK signal is issued,
iChip requires 4 seconds to complete the reset cycle before commands can be issued.
When iChip is configured for auto baud rate, the BREAK method is especially useful to
force iChip back into auto baud rate mode when iChip and the host lose synchronization.