Flow Control - ZyXEL Communications U-336S User Manual

Flow Control

In extended fax AT command mode, the U-336S always uses
hardware (CTS/RTS) flow control. The flow control signaling used
sending a fax is:
• CTS is used by your modem for DTE flow control. When the
modem turns CTS off, the buffer inside the modem is full and
cannot accept any more data. The computer should send data
only when CTS is ON.
• RTS is used by the computer to signal your modem that the fax
message is finished. As soon as RTS off is detected, the modem
starts the post message handshaking to make sure that the
remote facsimile has received the fax message successfully.
Then it hangs up the phone and sends a status report to the
DTE.
If you want to send a multi-page fax, just add the RTC signal
between the fax message of two pages. The modem detects the
RTC signal automatically, handshakes the multi-page procedure
with the remote facsimile and sends the next page.
The following flow control signaling is used while receiving a fax:
• CTS is not used when receiving fax.
• RTS is used to inform your modem that the computer cannot
accept data at this moment. The modem will not pass received
data to the DTE if RTS is turned off.
When finished receiving the fax message, your modem will turn off
CD then send a status report result code to the DTE.
Fax Operation 83