Rockwell Automation 61C345 4 Input 4-20mA Analog Rail Module - Manual (Page 30)

4Ć8
17 16 15 14 13 12 11 10 7 6 5 4 3 2 1 0 Octal
12 bits of converted analog data
overĆrange (1=overĆrange)
underĆrange (1=underĆrange)
not used
not used
Figure 4.8 Ć Local Head Register Image for Input Channels
The Analog Rail module data may also be accessed in the middle of
the scan (as opposed to the end of the scan) using the appropriate
number of Analog In (AIN) blocks. The AIN block will set the
overĆrange or underĆrange bits if applicable. See section 4.1.4 for
more information about the AIN blocks.
Note that the AIN block is supported by the AutoMate 20E
(M/N 45C224 and 45C225), but not the AutoMate 20 (M/N 45C20,
45C21, 45C220, 45C221) by APX Version 3.0.
For processors that do not support the AIN block, you can use the
MOVE block to move data in and out of the registers assigned.
OverĆrange and underĆrange bits should be used as inputs to error
coils. The I/O update will occur automatically at the end of each
scan. See Appendix C for a sample AutoMate program that reads
from the Analog Rail module without using the AIN block.
4.1.4 Analog In (AIN) Instruction Block
The AIN block is used to read inputs from the Analog Rail module.
AIN is supported for the A20E. The AIN block makes it possible to
update the channels on the Analog Rail module during the scan
instead of at the end of the scan (the standard AutoMate I/O
update). The block also makes it possible to update all four
channels during the scan in Rail mode, a hardware configuration
which would otherwise allow only one channel on the module to be
updated. The format of the AIN block is shown in figure 4.9.