Rockwell Automation 1747-L55x,D174710.4 SLC 500 Ethernet - Manual (Page 33)

4–3 Communicating on the Ethernet Network
Publication 1747-10.4
Control Block Layouts
The SLC 5/05 MSG control block length varies with the type of
communication and with the addressing you use. Control block
layouts are shown for:
•
SLC 5/05 Channel 1 (Ethernet port)
MSG Control Block without Logical ASCII Addressing
•
SLC 5/05 Channel 1 (Ethernet port)
MSG Control Block with Logical ASCII Addressing
valid for PLC-5 typed read or write only
The AO bit (word 12, bit 15) is used for PLC-5 type reads and
writes. If AO bit is reset to 0, then logical binary addressing is used
for PLC-5 type reads and writes. If AO is set to 1, then logical
ASCII addressing is selected; in this case the processor expects the
ASCII address string information to be stored in words 14 to 55 of
the MSG control block (see control block layout on page 4–5).
The AO bit has no meaning for 485CIF and 500CPU types of reads
and writes.