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06.91
9.3
XON/XOFF procedure
If a monitoring time (device, character monitoring time or line reservation time) has expired, the
driver sends the XOFF character and goes into the initial state.
The configuring parameter "Node states equal" is insignificant unless both stations want to
transmit at the same time. The node configured with "Node states equal=Yes" is the master
and is entitled to interrupt the transmission initiated by the other node to transmit its data.
Optionally, both nodes can be configured as master. In this case, they have the same priority
and neither of them can interrupt or be interrupted during transmission.
a) Configuration: Node states equal:
Waiting for 1st XON:
Data output
CP 315
XON/XOFF procedure
Transmission job of
COM area
.
.
.
.
1st character
2nd character
. .
.
120th character
.
.
.
.
121st character
122nd character
. .
.
nth character
(EI)
© Siemens AG 1989 All Rights Reserved
SINUMERIK 840/880 (PJ)
t < Waiting period for 1st XON
t < Device monitoring time
6FC5 197-0AB20-0BP0
9.3 XON/XOFF procedure
No
With (EI)=End identifiers, if configured
Peripheral unit
(e.g. printer)
XON
XOFF
XON
9 Appendix
e.g.
printer
buffer
full or
off-line key
pressed
9–13
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