User Manual Owner's manual

Block Transfer
Chapter 18
18-8
RunTime Errors
Misuse and/or inadvertent changes of instruction data can cause run-time
errors when:
The module address is given a non-existent I/O rack number.
A read transfer overruns the file into a processor work area or into user
program by an inadvertent change of the block length code.
Block transfer reads data from an I/O module into the processor’s input
image table in one I/O scan.
Programmed as an output instruction.
Block length depends on the type of module you are using.
Request for transfer is made in the program scan.
I/O scan is interrupted for the transfer.
Done bit remains on for one scan after a valid transfer.
Instruction requires two words of the data table.
Figure 18.5 shows an example rung containing a block transfer read
instruction and the data table areas used by the instruction.
Block Transfer Read