40 VMIVME-1184* 32-bit Optically Isolated Change-of-State (COS) Input Board
Publication No. 500-001184-000 Rev. B.0
Figure 3-2 Leading Edge Example
Figure 3-3 1x Counter Mode
Figure 3-4 2x Counter Mode
3.11.2 2X Quadrature Mode
If input A leads input B, the module counts up on both rising and falling edges of
input A. If input B leads input A, the module counts down on both rising and
falling edges of input A. This mode is set through CSR1 Bits 5 and 4.
CRS1_[5] = 1
CSR1_[4] = 0
Figure 3-5
illustrates the relationship between inputs A and B and the count value
in the 2X quadrature mode.
Figure 3-5 2X Quadrature
A
B
“A leading B” example
A
B
“B leading A” example
All rising edges of “A” increment counter
1
2
3
A
B Ignored in this mode
Any edges of “A” increment counter
1
2
3
A
B Ignored in this mode
4
2X Quadrature
Current Value
A
B
25µs
min
26.7µs
min
1
2
3
4
1
2
3
0
Counts Up
(A Leading)
Counts Down
(B Leading)
0
1
2
3
4
3
2
1
0
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