Rockwell Automation 1747-BSN Backup Scanner Module - Manual (Page 133)

Publication 1747-UM010B-EN-P - September 2003
RIO Block Transfer 7-21
Comparison to the PLC-5 BTR and BTW
Block Transfer Reads and Writes in SLC processors are quite similar to
the instructions in the PLC-5. However, some differences exist
between them, as shown in Table 7.5 on page 7-21.
Table 7.5 Block Transfer Comparison
SLC PLC-5
Control Block 3-element integer (N) type 5-element integer (N) type
or 1-element block transfer
(BT) type.
EN (Enable Bit) Follow BT rung state. Gets set when BT rung goes
true. Remains set until the
BT finishes or fails, and the
BT rung goes false.
NR (No Response bit) None This bit is in control block
word 0, bit 9.
CO (Continuous bit) None This bit is in control block
word 0, bit 11.
FILE (File Number) None This word is control block
word 3.
ELEM (Element Number) None This word is control block
word 4.
Error Codes 7 error codes 11 error codes
BTR/BTW number limitation
for one scanner/channel 32 64
BT Status Bits Can only change when BT
rung is scanned. Can change at any point in
the program scan.
IMPORTANT
Do not manipulate the I/O image words of the RIO
scanner for modules to which you are block
transferring. These words are used by the RIO
scanner and the remote device as block transfer
handshake bits. Any manipulation of them by the
user program while a block transfer is in progress
causes the block transfer to fail.