Verilink AS100 (896-502379-001) Product Manual - Manual (Page 92)

6-18 Access System Centum Series User Manual
Printer Port Flow Control
The Centum Series port supports simultaneous hardware and software
flow control signaling from the attached device. The hardware control is
RTS if connected directly to a printer or CD if connected via a modem.
The software control is XOFF/XON. The XOFF is DC-3
(Cntl-S); however, any character arriving at the port is treated as an XO
(to protect against a damaged DC-1).
Hardware control has priority: If RTS (or CD) is low, transmission to the
device will be suspended and the data will be buffered in Centum Series.
Receipt of software flow control characters while RTS (or CD) is low will
have no effect on the port. Transmission will be resumed when RTS (or
CD) goes high.
If the port receives an XOFF while RTS (or CD) is high, transmission will
be suspended and the data will be buffered. Transmission will be
resumed if any subsequent character (including another XOFF) is
received or if RTS (or CD) is lowered and subsequently raised. This
mechanism protects against a “lost” XON.