Specifications

AN93
Rev. 0.9 99
XON/XOFF is a software flow control in which the
modem and the terminal control data flow by sending
XON characters (^Q/11h) and XOFF characters (^S/
13h). XON/XOFF flow control is enabled on the Si2493/
57/34/15/04 with AT\Q4.
DCD
does not de-assert during a retrain (see S9 for
carrier presence timer and S10 for carrier loss timer).
CTS
always de-asserts during initial training, retrain,
and at disconnect regardless of the \Qn setting. For \Q0
CTS, flow control is disabled, and CTS
is inactive during
data transfer. The modem remains in the data mode
during normal automatic retrains. The host can force a
retrain by escaping to the command mode and sending
ATO1 or ATO2.
Figure 16. Transmit Data Buffers
Figure 17. Receive Data Buffers
796 Characters
128 Characters
1024 Character Elastic Tx Buffer
SRAM
CTS Deasserts
CTS Asserts
Transmit
14-Character
Hardware
Buffer
Tx Data
CTS
796 Characters
128 Characters
1024 Character Elastic Rx Buffer
SRAM
Receive
12-Character
Hardware
Buffer
Rx data
RTS
RXF bit
REM bit
Parallel
Mode