Rockwell Automation 1771-IS 5V DC INPUT MOD - Manual (Page 36)

Programming and Operation
Chapter 3
3-17
Programming Considerations, PLC-2 Family
The block transfer data address is the address that identifies the block
transfer instruction. Care should be taken when assigning these addresses
in the data table.
Date Address (PLC-2 Family)
The data address for a block transfer instruction should be the first
available address in the timer/counter accumulated area of the data table.
This address is 030
8
for the Mini-PLC-2 or -2/15. For the PLC -2/20 or
-2/30, this address depends on the number of I/O racks connected to the
processor module, i.e. address 020
8
for 1 I/O rack, 030
8
for 2 racks, etc. to
070
8
for 6 racks and 200
8
for 7 racks. When more than one block transfer
module is used, the data addresses should be consecutive.
Data Address Boundary (PLC-2 Family)
A boundary word containing zeros should be entered in the data table
following the last block transfer data address. When the processor sees
the boundary word, it terminates the block transfer search routine so that
subsequent data table values are not interpreted as the rack, module group
and slot numbers associated with block transfer data addresses.
Block Transfer Programming, PLC-3
The processor transfers switch status data from the module to the data
table by a block transfer read operation. The following information must
be specified in order to program block transfer with the PLC-3 processor.
Values entered in parentheses correspond to the programming example in
paragraph titled “Programming Example PLC-3” and Figure 3.9.