Rockwell Automation 1770, D17706.5.16 Ref Mnl DF1 Protocol Command - Manual (Page 118)

7–31 Communication Commands
Publication 1770Ć6.5.16 - October 1996
Important: The interface module at the receiving PLC node
executes this command by first making a copy of the
addressed PLC byte. It then sets or resets the
appropriate bits and writes the byte back into PLC
memory. At the same time, the PLC processor can be
changing the states of the original bits in memory.
Because of this, some data bits may unintentionally be
overwritten.
unprotected read
1774-PLC, PLC-2, PLC-3, PLC-5
Reads words of data from any area of PLC and PLC-2 data table
memory. In PLC-3 and PLC-5 processors, the data is read from the
PLC-2 compatibility file. Use the SIZE field to specify the number
of bytes to be read. To specify a number of PLC words, SIZE should
be an even value because PLC words are two bytes long. Data bytes
are transferred low byte first. The address of a word should be even.
C
CMD
01
STS TNS ADDR SIZE
R STS TNS
CMD
41
DATA (max. 244 bytes)
DST SRC
SRC DST
SLC 500, MicroLogix 1000
Reads data from a common interface file (CIF). The SLC 500 CIF is
data file number 9, the MicroLogix 1000 CIF is integer file 7. This
command is implemented as a protected file read in SLC processors
and is used by non-SLC 500 devices to read information from
SLC 500 devices.
C
CMD
01
STS TNS ADDR SIZE
R STS TNS
CMD
41
DST SRC
SRC DST DATA
Address - Logical offset into the CIF.
SLC 500, SLC 5/01 and SLC 5/02 (SLC 5/02 prior to series C FRN 3) processors use word addressing
SLC 5/02 series C FRN 3 and later, SLC 5/03, and SLC 5/04 processors select word or byte addressing
for S:2/8 = 0 (default) Ċ word addressing is used
for S:2/8 = 1 Ċ byte addressing is used
Size - Number of bytes to read starting from the offset.
for SLC 500, SLC 5/01 and SLC 5/02 processors: valid range is 0 Ć 95 bytes (odd or even)
for SLC 5/03 and SLC 5/04 processors - with internet protocol: valid range is 0 Ć 225 bytes (odd or even)
- without internet protocol: valid range is 0 Ć 236 bytes (odd or even)
• 1774ĆPLC
• PLCĆ2
• PLCĆ3
• PLCĆ5
• SLC 500
• SLC 5/03
• SLC 5/04
• MicroLogix 1000