Balluff BIS U-4A7-082-01C-07-S4 Betriebsanleitung Seite 161

BIS U-4A7-082- _1C-07-S4
Industrial RFID system - Read/write head
8
System integration (continued)
Process data cycle
A process data cycle consists of the complete
transmission of the input and output data. In each case,
10 or 32 bytes of input and output data plus two bytes of
command data are transmitted.
Higher-level bus
system
IO-Link
BIS U
Data carrier
IO-Link-PD-cycle
PD-cycle
Fig. 8-2: Timing of IO-Link transmission
1. The command is passed on from the controller to the
IO-Link master via a bus system.
2. After the synchronization time t1, the command is
transmitted to the BIS U via IO-Link. The duration
depends on the bus system, the master, the cycle time
and the current state of the IO-Link communication
(see problem described above).
3. Once the command has arrived at the BIS U, the
processing time begins. This consists of the time for
command processing t2, the time for the actual
reading process t3 and the evaluation time for the read
data t4. A flat value of maximum 3 ms can be allowed
for t2 and t4. Please note: If the data carrier to be read
has already been detected by the device, then the time
for data carrier detection is omitted.
4. Here the time t3 of the actual data carrier processing is
shown (see chapter 5.12 on page 18).
5. After a renewed synchronization time t5, the first data
is passed on to the IO-Link master with the next
in-data cycle. In addition, the AE bit is set in the bit
strings. The time for this is t7 = 1 x cycle time.
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6. The data is forwarded to the controller via the higher-
level bus system. The latency time t6 depends on the
bus system and IO-Link master.
7. Once the first data has arrived at the controller, the
toggle bit in the output buffer must be inverted (see
chapter Output buffer on page 39). In the example, it
is assumed that this happens immediately and that the
transmission to the IO-Link master is fast enough for
the BIS U to receive the new data immediately with the
next out-data cycle.
8. Now the device puts the next and thus the last bytes of
the read data into the input buffer and inverts the
toggle bit.
9. The controller retrieves the data and deletes the AV bit.
10. The output buffer, updated again, is sent to the BIS U.
11. The device terminates the read command and deletes
the bits belonging to the assignment in the bit strings in
the input buffer.
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