BECKHOFF BK8000 - Manual (Page 21)

RS 485 Coupler BK8000
BK8000 21
Request
The following data must be transferred in the request (output data to the
coupler) from the master to the slave (BK8000):
Byte 1:
0x50 (´P´) Start identifier
Byte 2: 0x03 3 output data words
Byte 3: 0x12 Any selectable message ident
Byte 4: 0x05 Set bus coupler address
Byte 5: 0xXX Data byte 0
Byte 6: 0xXX Data byte 1
.
.
.
Byte 9:
0xXX Data byte 4
Byte 10: 0xXX Dummy byte
Byte 11: 0x?? Checksum calculated on the basis of the
bytes (1-10)
Response The bus coupler then sends the following response (input data of the bus
coupler):
Byte 1:
0x70 (´p´) Start identifier
Byte 3: 0x05 3 input data words
Byte 4: 0x12 Returned message ident
Byte 5: 0x00 Master address 0
Byte 6: 0x?? Status byte
Byte 7: 0xXX Data byte 0
Byte 8: 0xXX Data byte 1
.
.
.
Byte 12:
0xXX Data byte 5
Byte 13: 0x?? Checksum calculated on the basis of the
bytes (1-12)
Watchdog The bus coupler has a watchdog timer that is set by default to 1 s. The
watchdog is triggered if no valid data exchange with the bus coupler has
taken place after the expiry of this Watchdog time. The digital outputs are
then all set to logical '0' and the analog terminals assume a user-defined
status (by default, they are set to logical '0'. The input data is frozen at the
last value. The bus coupler's watchdog time can be set using the Beckhoff
KS2000 configuration software.