Figure 21 Serial Port Flow Control Xon/Xoff - Ithaca 150 Programmer's Manual

Programmer's Guide
Communications
port
Serial
data in
Inquire
Serial
commands
data out
Send
DTR
Send
Send
RTS
XON or XOFF
(Not used for
flow control)
RTS -> Request to send

Figure 21 Serial port flow control XON/XOFF

12/14/99
PcOS Series 150
Serial Port Flow Control
XON/XOFF
High
ENQ
Data
speed
Data
Proc.
FIFO
ENQ response
XOFF
Buffer filling up
Buffer emptying
XON
Select key
Rev G
Print
Data
Data
buffer
256 - 6K
DTR -> Data terminal ready
Communications
Serial Port
Printer
control
software
Page 119