Allen-Bradley FLEX I/O 1794-ID2, Руководство пользователя, Страница: 17 / 84

1–7 Overview of the Incremental Encoder Module
Publication 1794-6.5.15 – December 1998
Preset Function
Use the preset function to copy a value from the preset register to the
counter register.
Counter Register
Counter Register
Preset Register
Logic
PresetEnable = 1
Preset
Z =
Preset Register
PresetReached = 1
PresetReached = 1
Method 1
Method 2
The flag PresetReached is set when the counter register and the
preset register are equal (if the counter preset is reached, or if the
counter has been loaded with the preset value). This flag is reset on a
positive edge of PresetReset after the operation and can only be set
after at least one additional counting pulse.
Gate Function
Use the gate function to determine when counting starts and
stops.You can use this function to measure distance.
The parameter GateControl determines the gate function. The gate
signal is connected to input G. It is a 2–bit binary code in write word
1 or 2, bits 09 and 10
Word
1 or 2 Gate Control Function
1 or 2
Bits
09–10
Binary 10 09 Gate Control bits
09–10
0 0 0 No gate function on input G (Count is independent)
1 0 1 Counting only if G = 1 (active)
2 1 0 Counting only if G = 0 (inactive)
3 1 1 Calibration if G = 1 and all other conditions are
fulfilled (refer to Calibrating the Module, chapter ?).
Gate Control = 1
Counter Register
Logic
A
G = 1
The counter is counting if G = 1.
Example
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