Allen-Bradley PLC-5 User Manual

Publication 1785-UM012D-EN-P - July 2005
Communicating with Remote I/O 6-13
Transferring Block Data
In addition to discrete data, the controller can also exchange block data with
remote I/O. Block-transfer instructs the controller to interrupt normal I/O
scanning and transfer as many as 64 words of data to/from a selected I/O
module. The figure below shows how the scanner-mode controller handles a
block-transfer.
Block-Transferring Data to Controller-Resident Local, Extended-Local, and
Remote I/O
15299
Rack 7
Controller-
Rack 0
Remote I/O
Scan
Remote I/O
Program
Scan
Rack 6
Rack 5
One transfer per
I/O scan
One transfer per
I/O scan
One transfer per
I/O scan
BTR or BTW Data
BT
Requests
Q
A
BTR or BTW Data
BT Requests
Q
A
BTR or BTW Data
BT Requests
Q
A
BTR or BTW Data
BT
Requests
Q
A
Q = Queue
A = Active
Buffer
I/O Scan
Multiple
Block Transfers
Q
A
One transfer per
I/O scan
BTR or BTW Data
Extended-
Local
I/O Scan
Adapter
Adapter
Adapter
BT Requests
Interrupt from STI or Fault Routine
The adapter used in the remote I/O scan is the 1771-ASB.
The adapter used in the extended-local I/O scan is the 1771-ALX.
Resident
Local
Local
Local
Rack 4
Racks 2
and 3
Rack 1
Adapter
Adapter
Adapter
per I/O Scan
Logic
Scan
1
1
1
1
1
1
2
3
2
3

Allen-Bradley PLC-5 Specifications

General

Brand	Allen-Bradley
Model	PLC-5
Category	Controller
Language	English