Rockwell Automation 1771-DB BASIC MODULE - Manual (Page 220)

Chapter
Call Routines 0–68 12
12 -30
2. The ladder logic program of the PLC processor must latch the output
image table, bit 11 or bit 13 to inform the BASIC module that valid
data is available. Bit 11 indicates that data is available for PRT1 and
bit 13 indicates that data is available for PRT2.
Latch Output Image Table
Bit 11 or 13
PLC Processor
BASIC Module
PLC Backplane
PRT2
PRT1
3. The BASIC module sets the input image table bit 11 or bit 13 to
inform the PLC processor that the BASIC module is ready for the
transfer.
Set Input Image Table
Bit 11 or 13
PLC Processor
BASIC Module
PLC Backplane
PRT2
PRT1
4. The BASIC module automatically transfers the data to the destination
serial port (PRT1 or PRT2) from the BTW buffer and performs the
block transfer.
PLC Processor
BASIC Module
PLC Backplane
PRT2
PRT1
DATA BUFFER
BTW Buffer
BYTE
COUNT
Reserved
5. The ladder logic program of the PLC processor unlatches output
image table bit 11 or bit 13.
Unlatch Output Image Table
Bit 11 or 13
PLC Processor
BASIC Module
PLC Backplane