Communication Between "Intelligent" (Equal) Nodes - Siemens SINUMERIK 840 Planning Manual

06.91
3.3.3.2

Communication between "intelligent" (equal) nodes

In the initial state, both nodes are ready to send and ready to receive; no control characters
are transmitted. The procedure does not prevent any initialization conflict (both stations
simultaneously attempt to send). This must be achieved by the application. In addition to the
control characters XON and XOFF, the STX character is recognized as a control character.
If a node that is configured as slave receives an STX character during transmission, it stops
transmitting and waits for the receiving job. This receiving job must arrive within a specified
waiting period (line reservation time). If the waiting period expires without a message being
received, the station goes into the initial state.
The transmission job interrupted by STX is then resumed.
Minimum wiring required for the XON/XOFF procedure
Transmitter
TxD
RxD
Signal ground
© Siemens AG 1989 All Rights Reserved
SINUMERIK 840/880 (PJ)
Receiver
RxD
TxD
Signal ground
6FC5 197-0AB20-0BP0
3 Interface Modules
3.3.3 XON/XOFF procedure
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