Event-Oriented Data Exchange; Status Information In The Process Data Channel - Bosch Rexroth ID 40 Manual

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Bosch Rexroth AG, MIT: ID 40, 3 842 530 344/2014-05
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8.4 Event-oriented data exchange

Event-oriented data exchange transmits data provided by the unbuffered prefetch
(Chapter 6.4.1.1 "Unbuffered prefetch"). The event-oriented data is purely input data
for the application and transmitted through the Interbus process data channel.
The process data channel (PD channel) is mapped in the I/O field of the application
(e.g., PLC) and is the default communication with general I/O bus users.
In the ID 40/SLK-IBS, the PD channel consists of six data words, or 96 bits. The
assignment of the process data channel is described in the following sections.
Unassigned bytes in the PD channel transfer the value 0.
8.4.1

Status information in the process data channel

The first two bytes in the event-oriented data exchange are status bytes with the
following structure:
Table 21: Status byte 0 of event-oriented data exchange
Byte 0 (bits 0–7)
7 6
Event counter
Bits 0 to 3 comprise the result code. The coding for the error code is the same as for
command-oriented data exchange (see Chapter 8.7 "Interbus error codes").
Bits 4 to 7 comprise the event counter. The counter runs cyclically from 0 to 15 and
is increased by 1 when the current PRECONNECTED link state is ended. This signals
to the control system that the data from the prefetch parameterization is updated.
At this point, the user program can import prefetch data. The counter also increases
when no prefetch is parameterized.
The following functions have been completed when the counter value changes:
• Pretransmit data has been entered in the MDT (if parameterized)
• Prefetch data was read from the MDT (if parameterized) and is ready to be
imported to a PLC DB
• If auto reconnect is active, the MDT was closed and the link state is CONNECTING
• If auto disconnect is active, the MDT was closed and the link state is
DISCONNECTED
• If no auto mode is active, the link state is CONNECTED. Data can be exchanged
with the MDT.
Table 22: Status byte 1 of event-oriented data exchange
Byte 1 (bits 0–7)
7 6
Actual link state
5 4 3
5 4 3
Data
transfer
status
2 1 0
Error code
2 1 0
Prefetch Prefetch Operative
param. param- flag
open eterized