Multi-Tech Systems MT2834MR6 - Manual (Page 49)

49
Chapter 3 - AT Commands
3.12 Flow Control Commands
Flow control refers to the techniques used by data terminal equipment and the modem to pause and resume
the flow of information between them. It prevents a device from accepting more data than it can handle. The
modem implements flow control in both directions. When the modem halts the flow of data, it is called flow
control, and when the computer halts the flow, it is called pacing.
&BSn Maximum Reliable Block Size
n = 0 or 1
Default: &BS1
When the modem is in reliable mode, use the &BS command to set the maximum size of a
data block. MNP Class 3 sends a 64-character block, while Classes 4 and 5 normally send
blocks of 256 characters or less. Reducing the block size for MNP 4 and 5 may improve
overall throughput whenphone lines are noisy; however, it also could slow data transfer if
line quality is good.
&BS0 sets the maximum transmit block size to 64 characters.
&BS1 sets the maximum transmit block size to 256 characters.
$EBn Asynchronous Word Length
n = 0 or 1
Default: $EB0
The MT2834MR6 can operate with either a 10-bit format (one start bit, seven data bits, one
parity bit, and one stop bit) or an 11-bit format (one start bit, eight data bits, one parity bit,
and one stop bit) in both command and online modes.
$EB0 enables a 10-bit format It automatically detects parity when an AT command is
issued.
$EB1 enables an 11-bit format.
&E3 Flow Control Disable
The &E3 command completely disables data flow control initiated by the modem.
&E4 Hardware Flow Control
Factory default. The &E4 command enables the modem’s use of the Clear to Send (CTS)
signal on the RS-232/V.24 interface to regulate data flow. When CTS drops, data flow is
suspended until the signal goes high again. This method of flow control works in
conjunction with pacing (i.e., computer-initiated flow control), which uses the Request to
Send (RTS) signal on the RS-232/V.24 interface. Hardware flow control cannot be enabled
unless an active error correction protocol is selected.