Rockwell Automation 1771-DB BASIC MODULE - Manual (Page 235)

Chapter
Call Routines 0–68 12
12 -45
3. When data is available, the BASIC module transfers the data into
BTR buffer. The DH-485 status word is placed in lower byte of
word 1. The upper byte of BTR word 1 is reserved.
BASIC Module
DATA 2–64
BTR Buffer
Status 1 Reserved
4. The BASIC module sets the input image table, bit 14 and performs a
block transfer read.
PLC Processor
BASIC Module
PLC Backplane
Set Input Image Table
Bit 14
5. The local PLC receives the data and status from the block transfer
and then resets output image table bit 14 to inform the BASIC
module that it received data.
PLC Processor
BASIC Module
PLC Backplane
Resets Output
Image Table
Bit 14
6. The BASIC module resets the input image table bit 14 on the same
end of scan cycle in which the block transfer was completed.
PLC Processor
BASIC Module
PLC Backplane
Reset Input
Image Table
Bit 14