Advanced Functions; Handling Oversize Packets - Comtrol DeviceMaster PNIO 2000 Series User Manual

Handling Oversize Packets

DeviceMaster PNIO | UP User Guide: 2000639 Rev. A

Advanced Functions

This section discussed the following topics:
• Handling Oversize Packets
• Shared Device Functionality
When a packet larger than the input size of the submodule is received, the
DeviceMaster's default behavior is to truncate the packet to the maximum allowed
size and send it to the IO controller as normal IO data. The length field is not
changed when a packet is truncated. The IO controller can determinate if a packet
has been truncated by checking the length field. If the length field is greater than
the submodule input size, then the packet has been truncated.
The DeviceMaster supports two other options for oversize input packets received
from serial or Ethernet device. These are the options Oversize Rx Packets.
• Truncate (default) - Oversize packets are truncated and send to IO controller
as cyclic IO data.
• SaveRec - Oversize packets are truncated and send to IO controller as cyclic IO
data. The original packets are also saved as acyclic record data.
• Drop - Oversize packets are dropped.
When the SaveRec option is selected, an oversize packet is truncated and sent to
the IO controller via normal cyclic IO update, just like the default behavior.
Besides, the original packet is also be stored as an acyclic record data and
available for record data read. The following record indexes are used to read the
saved oversize packet.
Record Indexes for
Oversized Rx Packets
10000 .. 10000+N-1
The following figure shows the read data record instruction (RDREC) and the
table lists its parameters. For more information regarding the RDREC instruction,
refer to TIA Portal help system.
on Page 95
on Page 99
Description
Saved oversize packet for an specified input
submodule.
Where, N is the size of the saved oversized packet,
including the 4-byte sequence number and length
field followed by the actual input data, the same
format as shown in the table of an Input Data
Format of an Input Submodule (Page 81).
Advanced Functions - 95