Rockwell Automation 2705 REDIPANEL KEYPAD MODULE USER MANUAL - Manual (Page 49)

Chapter 7
Programming
7–11
A 1771–SN, Sub I/O scanner may be used with a PLC–5 family processor
when the application requires more remote devices than that processor can
accommodate. The sub I/O scanner module may be used to communicate to
as many as 16 additional remote I/O devices.
The 1771–SN Sub I/O scanner may be located in the same rack as the PLC–5
(the local rack), or in any space of the remote racks supported by the
processor. The PLC–5 communicates to the sub I/O scanner using block
transfer read and write instructions, this method is called Bidirectional Block
Transfers.
The block transfer read instruction, reads input data from the sub I/O scanner
and transfers that data to integer files in the PLC. The block transfer write
instruction, writes output data to files of the PLC, then transfers that data to
the sub I/O scanner. What this means is that instead of input addresses
starting with “I:” and output addresses starting with “O:”, both input and
output addresses will begin with “N7 or greater:”. The rest of the input
addresses will depend on the specific integer file that is designated as the
“DATA FILE” in the block transfer read instruction. The rest of the output
addresses will depend on the specific integer file that is designated as the
“DATA FILE” in the block transfer write instruction.
The Keypad Module must have Bank #1 DIP Switch settings set for PLC–2
even though a 1771–SN scanner is used with a PLC–5. Refer to Page 5–2
for additional information.
Using PLC-5 Controllers and a
Sub I/O Scanner with Keypad
Modules