Rockwell Automation 1794-IJ2XT FLEX I/O Frequency Input Modules User Manual - Manual (Page 76)

Publication 1794-6.5.11 - September 2011
66 Program Your Module with PLC Processors
PLC-2 Family Processor
The 1794 Frequency I/O module is not recommended for use with PLC-2
family programmable controllers due to the number of digits needed for high
resolution.
PLC-3 Family Processor
Block transfer instructions with the PLC-3 processor use a control file and a
data file. The block transfer control file contains the data table section for
module location, the address of the block transfer data file and other related
data. The block transfer data file stores data that you want transferred to the
module (when programming a BTW) or from the module (when programming
a BTR).
The programming terminal prompts you to create a control file when a block
transfer instruction is being programmed. The same block transfer control file
is used for both the read and write instructions for your module. A different
block transfer control file is required for every module.
IMPORTANT
The frequency input module functions with reduced
performance in PLC-2 systems. Because the module does not
support BCD and the PLC-2 processor is limited to values of
4095 (12 bit binary), many values returned in the BTR file may
not provide meaningful data to the PLC-2 processor.