Roland R1000 Series Manual page 88

Communication with the PLC
Checksum
The checksum is formed of the bytes 1 – 6.
Meaning
Bit
Checksum
The checksum of bytes 1 - 6 is calculated and the least significant byte of the result is inserted into
byte 7.
6.4.2 Service "Open parameter channel"
The service open parameter channel is initiated by the master with the selection of the service. The
content of the index bytes I1, I2 and the application data bytes 0 through 3 are not relevant. The
checksum of bytes 1 through 6 is calculated and inserted in byte 7. To initiate the service the
master changes the handshake bit.
To avoid data fault the following sequence is compulsory:
1. Service selection, program index, parameter index
2. Switch handshake
In addition consistent data transmission from master is necessary.
The R1000 checks the data with the checksum and mirrors the application data, the service
selection and the index selection into O1, O2.The R1000 sets the handshake bit in O0.0 only in the
last step and signals thereby that the data is valid. This sequence is observed by the R1000 in
order to avoid data faults.
The slave should ensure a consistent data transmission.
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88
Double Sheet Detector R1000 series UDK20
with integrated fieldbus interface
Checksum byte
0 1 2 3 4
x x x x x
Note For the service "Open parameter channel" the index bytes I1,I2 and the
application data bytes I3... I6 are not relevant.
Attention If reading cannot be executed the collision bit is set. The fault number
is transmitted instead of application data, see section "6.4.8 Reset
faulty access". The collision bit can be deleted with one of the
following services: Close parameter channel, Empty service or Reset
parameter channel.
Manual
Checksum
Notes
5 6 7
x x x Checksum of data communication bytes 1 - 6
B0048191 / Rev. 1.5