BECKHOFF C1300 - Manual (Page 35)

C1300 VME to II/O Interface Unit Beckhoff II/O-System
Date : 18.12.95 Version : 2.01 Page 35 of 44
Function 12h: Free running communication
Function 12h enables a free running communication, which is executed by the
interface without a trigger of the VME system. The usual handshake to
synchronize communication and process image control via the GCB is not
necessary.
Channel Length Function Argument 0 Argument 1
Request 04 12 k pan
Channel Length Function Argument 0 Comment
Reply 03 12 00 00 says: ok
03 12 01 01 says: erroneous data
with:
pan process image number
k Command code
0 = disable free running
communication
1 = enable free running
communication
It is highly recommended to use this mode only with byte - oriented I/O functions,
due to the fact that no deterministic behaviour exists between request and response
data and between two adajcent read or write access events of the VME Master:
The process image data might result from different communication cycles.