Rockwell Automation 61C346 4 Input 0-10V Analog Rail Module User Manual

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4Ć7

4.1.2

AutoMate Programming in Rail Mode

In Rail mode, the Analog Rail module is imaged in one I/O register of

the processor. Data from one of the four channels will occupy the

updated at the end of each scan. For input channels, the two channel

select bits in the register must be set to the appropriate input channel

number. After the I/O update, the register contains the data in the

format shown in figure 4.7.

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)
channel being read: LSB
channel being read: MSB

MSB

LSB

0 =

1 =

CH#

CH 0

CH 1

CH 2

CH 3

Figure 4.7 Ć Rail Mode 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, which is the normal

mode of operation for digital rail I/O) using the appropriate number of

Analog In (AIN) blocks. The AIN block will check whether the

overĆrange or underĆrange bits have been set by the module and the

error coil will be energized, if applicable. See section 4.1.4 for more

information about the AIN block.
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 and later.
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 and to

determine the channel select bits. 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 AIN blocks.