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9 Appendix
9.1 Reception using the 3964R procedure
Example : Error-free data communication with the 3964R procedure:
CP315
3964R procedure
DLE (NAK)
DLE (NAK)
Initialization conflict
If a device does not respond to a request to send (STX character) by its peripheral unit within
the timeout period with the acknowledgement DLE or NAK but also sends the STX character,
this means that an initialization conflict exists. The two devices wish to execute a transmission
task at the same time.
The device with the lower priority cancels its request and responds with the DLE character.
Then the device with the higher priority sends its data as described above. After release of the
connection, the device with the lower priority can execute its transmission task.
9–2
Peripheral unit
(e.g. AS 512, CP 525)
2nd character
© Siemens AG 1989 All Rights Reserved
STX
1st character
:
:
nth character
DLE
ETX
BCC
6FC5 197-0AB20-0BP0
SINUMERIK 840/880 (PJ)
08.89
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