Rockwell Automation 1771-DB Basic Module User Manual - Series A - Manual (Page 134)

Programming
Chapter 6
6–2
The BASIC Module also maintains a block-transfer-read (BTR) buffer that
is the value of the next block, read by the host processor. The BASIC
program initializes this buffer using CALL 5 and transfers the data to the
BASIC Module processor (for subsequent transfer to the host processor)
when CALL 7 or CALL 2 executes. You should complete the building of
the read buffer before initiating its transfer.
The following sample programs use block-transfer instructions. The
Mini-PLC-2 (cat. no. 1772-LN3) and PLC 2/20 (cat. no. 1772-LP1,-LP2)
processors use multiple GET instructions to perform block-transfers. Refer
to the processor user’s manual for an explanation of multiple GET
block-transfers.
This sample program (figure 6.1 and 6.3) assumes that the application
requires a single block-transfer-read (BTR) and a single
block-transfer-write (BTW) to pass data between the processor and the
BASIC Module (i.e. transfer of 64 words or less). If the transferred data
exceeds 64 words you must program multiple file to file moves to move
different data sets to and from the block-transfer files.
6.2.1
Block-Transfer-Write and
Block-Transfer-Read Buffers
(continued)
6.3
Block-Transfer with PLC-2
Family Processors
6.3.1
PLC-2 Processor Program