Rockwell Automation 1794-VHSC 1794 FLEX I/O Very High Speed Counter Module User Manual - Manual (Page 42)

34 Rockwell Automation Publication 1794-UM010D-EN-E - July 2013
Communicate With Your Module
moves decimal point left 2 places dividing the frequency value by 100; +1 moves
the decimal point 1 place, multiplying by 10, and so on. This allows frequency
values to fit in a single word.
Applying the Frequency/Resolution Enhancement
To use this mode, proceed as follows.
1. Power up the FLEX chassis, or put the controller into RUN mode, or
both. Let the 1794-VHSC module initialize as normal. Wait for the OK
indicator on the module to go solid green.
2. You must place ladder logic in your PLC that performs the following:
a. Set a value between -4 and +2 into output word 2 and/or 3.
b. Then set (1) the M11 bit in the upper byte of control word 0.
When the upper byte of the output word is not zero, the status
indicator flashes red, and the TF bit (bit 12, input word 8) is asserted.
c. Next, reset (0) the M11 bit in the upper byte of output control word 0.
Clearing the upper byte of output word 0 restores the module to an
operational state, clears the TF bit in input word 8 and returns the
indicator to green. The module is now in enhanced mode.
3. To turn this feature off:
a. Set output word 2 or 3 to zero (no value)
b. Set (1) the M11 bit
c. Then reset (0) the M11 bit
ATTENTION: Use this enhancement mode with caution since no
checks are performed to verify data. Unintended operation can occur.