User manual

Section 4

AT COMMAND SET

4-17

AT&H HELP

Parameters : 0 to 4

Default : None

This command displays several levels of help screens to reduce the need for a handbook to

enter field changes.

AT&H0 - General help Summary.

AT&H1 - Extended help Summary.

AT&H2 - Help on Dial Modifiers.

AT&H3 - Help on Test Commands.

AT&H4 - Help on S-Registers.

AT&I Constant Speed INTERFACE

Parameters : 0 or 1

Default : 1 (enable Constant Speed Interface)

The AT&I command allows the data rate of the DTE to be at a uniform rate, regardless of

the rate determined by the communication format (specified by ATFn). This is useful if the

DTE can only operate at a single speed and when error correction is enabled. It can also

control whether a connection will be established or rejected if the MNP negotiations fail.

AT&I0 - Disable Constant Speed Interface. The modem will autobaud on the DTE rate

before the call, but will change the interface speed to that of the actual line

connection as soon as the call is established. For example, if your terminal is set

for 2400 bps and the DPX-213 can only establish a link at 1200 bps, the

message "CONNECT 1200" will be displayed at the 2400 bps autobaud rate and

then the interface will change to 1200 bps. Therefore, the terminal speed must be

changed to continue without errors. Some communications packages read the

"CONNECT XXXX" message and can be instructed to change your DTE speed

automatically. Also, the 'pause'

+++

'pause' escape sequence will need to

be sent at 1200 bps to be recognised.

AT&I1 - Enable Constant Speed Interface. The data to and from the terminal will be at the

last autobaud speed regardless of the actual connection speed. DTE speeds above

2400 bps (or faster than the actual on-line rate) can cause data to enter the

modem faster than it can be sent to line. Therefore, unless the AT&K and AT&U

flow control commands are set, data may be lost in buffer overflows.

The AT&I1 command in conjunction with AT&E1 or AT&E2 (MNP-4 or MNP-5) ensures

a dial link will be established regardless of whether or not the remote modem can support

MNP.