HMS A8NDPV1 Instruction Manual page 45

Get Started
Proceed to issue the actual request using a function block from the lib_dpv1 library. Pick any
Dpv1WriteCh* function block, using different channels allows for simultaneous communication
to multiple slaves.
Receiving the response
If the request is completed successfully (bit wDone is ON), then perform a response read after a
delay of 500ms. Due to the nature of Profidrive acyclic communication, the response may not be
immediately available after execution of the request. Waiting a small amount of time significantly
increases the chance of receiving a response on the first try. Another solution is to keep executing
read requests, until a proper read request is received.
It should also be noted, that 240 bytes can always be read using the Dpv1ReadCh* function
blocks. This is the maximum allowed length of a response. In case of a shorter response, only the
available data will be read.
If the response is received successfully (bit rDone is ON), then the received data can be accessed
from DataRead. The format of a positive response is as follows:
Byte no.
0
1
2
3
4
5
6-7
A8NDPV1 PROFIBUS Option Board
GX Works2 (Q-CPU) Acyclic communication example
Description
Request ID
Request reference
No. of parameters
DO-ID
No. of values
Format
Parameter value
Value
0x01
0x01-0xFF (same as in request)
0x01
0x01
0x01
See data format type table
Byte swapped parameter value
35