Sample Plc Program Handling Oversize Packets - Comtrol DeviceMaster PNIO 2000 Series User Manual

Sample PLC
Program Handling
Oversize Packets
DeviceMaster PNIO | UP User Guide: 2000639 Rev. A
Notes:
• The of target range [0..3] always contains the sequence number and the
original packet length. Reading a partial packet will not change the length
field. The LEN parameter indicates the number of bytes that are actually read.
• The DeviceMaster only saves one oversize packet per port/device. If a saved
packet has not been read by IO controller, the following oversize packets will
still be truncated and sent to IO controller as normal IO data, however they
will not be saved as record data. The Error Saving as Record Data count on the
Diagnostics | Communication Stats page will be incremented.
• A saved packet can only be read once by IO controller. Whether the record read
reads the whole packet or only a part of it, the DeviceMaster clears the entire
packet after a successful record data read. Any parts of the packet that are not
read are lost.
• The minimum target range is 5 bytes, include 4 bytes sequence number and
length, plus 1 byte data. The data can start at any location by using INDEX =
10000 + offset, MLEN = 5.
• An invalid record data read, such as an INDEX that is outside of a packet
range, or there is no save packet, will increment the PLC Record Read Error
count on the Diagnostics | Communication Stats page.
The following figure shows a sample PLC program that detects oversize packets
and saves them to a data block using the RDREC instruction.
Advanced Functions
Advanced Functions - 97