Rockwell Automation 1771-IXE/D Thermocouple/Millivolt Input Module User Manual - Manual (Page 67)

Appendix
D
Publication 1771-6.5.130 Ć May 1999
Block Transfer (Mini-PLC-2
and PLC-2/20 Processors)
Programming multiple GET instructions is similar to block format
instructions programmed for other PLC–2 family processors. The
data table maps are identical, and the way information is addressed
and stored in processor memory is the same. The only difference is
in how you set up block transfer read instructions in your program.
For multiple GET instructions, individual rungs of ladder logic are
used instead of a single rung with a block transfer instruction. A
sample rung using multiple GET instructions is shown in NO TAG
and described in the following paragraphs.
Rung 1: This rung is used to set four conditions.
•
Examine On Instruction (113/02) – This is an optional
instruction. When used, block transfers will only be initiated
when a certain action takes place. If you do not use this
instruction, block transfers will be initiated every I/O scan.
•
First GET Instruction (030/120) – identifies the module’s
physical address (120) by rack, group and slot; and where in the
accumulated area of the data table this data is to be stored (030).
•
Second GET Instruction (130/060) – indicates the address of the
first word of the file (060) that designates where the data will be
transferred. The file address is stored in word 130, 100
8
above the
data address.
•
Output Energize Instruction (012/07) – enables the block
transfer read operation. If all conditions of the rung are true, the
block transfer read enable bit (07) is set in the output image data
table control byte. The output image table control byte contains
the read enable bit and the number of words to be transferred. The
output energize instruction is defined as follows:
•
”0” indicates that it is an output instruction
•
”1” indicates the I/O rack address
•
”2” indicates the module group location within the rack
•
”07” indicates this is a block transfer read operation (if this
were a block transfer write operation, ”07” would be replaced
by ”06”.)
Rungs 2 and 3: These output energize instructions (012/01 and
012/02) define the number of words to be transferred. This is
accomplished by setting a binary bit pattern in the module’s output
image table control byte. The binary bit pattern used (bits 01 and 02
energized) is equivalent to 6 words or channels, and is expressed as
110 in binary notation.
Multiple GET Instructions
- Mini-PLC-2 and
PLC-2/20 Processors