Rockwell Automation 1772-L8_LW_LWP_LX_LXP,D17726.5.8 User Manual - Manual (Page 286)

Block Transfer
Chapter 18
18-21
First Get Instruction
The first Get instruction (Figure 18.9) identifies the rack location of the
block transfer module. The location must be stored in the first available
address in the timer/counter accumulated value area of the data table,
starting with 030. When more than one block transfer module is used,
consecutive addresses must be assigned in this area.
As its “data,” the first Get instruction stores the location of the block
transfer module with the first digit as the rack number, the second as the
I/O group number, and the third as the slot number. The processor
searches the timer/counter accumulated area for a match of the module’s
rack, group, and slot number.
Important: Place a 2-slot module in a complete group. Do not overlap a
module group when using 2-slot addressing.
Second Get Instruction
The second Get instruction (Figure 18.9) must be assigned an address in
the timer/counter preset area of the data table, 100
8
words above the first
Get address.
As its “data,” the second Get instruction stores a data table address that
designates the beginning of the file area reserved for block transfer data.
During a read operation, data is loaded into consecutive word locations
starting with the designated file address. During a write operation, data is
sent to the module from consecutive word locations starting with the
designated file address.
Important: When you reserve an area for block transfer data, select an
appropriate address to ensure all block transfer data is located in one 100
word (octal) accumulated data storage area or preset area (Figure 18.10).
If you select an address so the block transfer data cannot be located in a
single 100 word (octal) area, the processor jumps 100
8
words to the next
preset or accumulated area. If you have timers or counters in these areas,
the block transfer writes over these values which may cause
undesirable operation.