74/176 Interbus
Bosch Rexroth AG
, MIT: ID 40, 3 842 530 344/2014-05
8.5 Commanded link state via process data channel
Data is entered in the SLK using PCP communication (see Chapter 8.3 “Command-
oriented data exchange”). Since PCP transfer takes a lot of time to transfer a byte,
the link request (see Chapter 5.3.2 “Commanded link state”) can also be sent to
the SLK through the process data channel. The outputs in the PLC are used to do
this (the inputs are used for event-oriented data exchange, see Chapter 8.4 “Event-
oriented data exchange”).
A trigger bit is used to enter the commanded link state in the SLK since the I/Os
are permanently exchanged through the PD channel. The trigger bit is not returned
in the input map (event-oriented data channel). The actual link state (see Chapter
5.3.1 “Actual link state”) indicates the result of the commanded link state. A signal
handshake via the trigger bit is therefore unnecessary.
8.5.1
Output map structure
Table 23: Output byte 0 of output map
Byte 0 (bits 0–7)
7
6
5
4
3
2
1
0
Trigger bit = 7, bits 4–6 reserved
Commanded link state
When switching
bit 7
(from 0 to 1 or 1 to 0), the value of bits 0 – 3 is entered in the
SLK commanded link state and executed.
SLK ignores bits 4 – 6.
The SLK also ignores the
remaining 11 output bytes
of the PD channel.
The trigger bit and the commanded link state value can be entered in the same PLC
cycle (simultaneously). Data consistency is ensured within a byte.
8.5.2
Sample sequence
In this example, the commanded link state CONNECT is first sent to the SLK,
followed by DISCONNECT.
1. Enter the value for CONNECT in the lower half-byte (bits 0 – 3) and switch the
trigger bit.
This puts the commanded link state CONNECT into effect in the SLK.
...
2. Enter the value for DISCONNECT in the lower half-byte and switch the trigger bit
again.
The new commanded link state DISCONNECT is implemented.
PROOF COPy 1 | 20.05.2014 | FOR INTERNAL USE ONLy
