Spectrum Controls SLC 500, User Manual

Page: 36 / 66

4-6 Chapter 4: Channel Configuration, Data, and Status
User’s Manual Pub. 0300181-07 Rev. A
Count Mode: (Configuration Bits 6-7)
The Count Mode bit selects 1 of 4 types of counter operation.
The
Unidirectional counter mode is configured as an Up or Down counter. The
module will support 8 unidirectional input channels. Every clock pulse
increments the counter.
NOTE
The direction of the count can be inverted by the COUNT DIRECTION
bit (see bit 12).
The
Bidirectional counter requires 2 channels inputs. In this mode one channel
is used as the counter input and the second channel is used to determine the count
direction. The counter will increment when the Direction input channel is a 1 and
will decrement the counter when the Direction input channel is a 0. Even
channels, 0, 2, 4, 6 are inputs. Odd channels, 1, 2, 5, 7 control direction. Both
channels within a pair must be configured for bidirectional mode. Bidirectional
encoding will report the same count value on each channel’s output.
When the counter is set to
Quadrature mode channels will be configured into
quadrature encoding pairs. Both channels within a pair must be configured for
quadrature mode. Quadrature encoding will report the same quadrature count
value on each channel’s output. Quadrature mode allows for the channels to
count up or down depending on the quadrature encoding direction. The COUNT
DIRECTION bit can invert the direction of the quadrature encoding. The QUAD
X1 mode clocks the counter once every quadrature cycle. The QUAD X4 mode
clocks the counter 4 times every quadrature cycle, once for every edge transition
on both input lines.
Table 4-3. Count Mode Settings
Mode Channels Bits Function
UniDirectional 8 00 Unidirectional Up/Down counter
BiDirectional 4 01 Bidirectional Up/Down counter
Quad X1 4 10 Quadrature Mode 1 count/cycle
Quad X4 4 11 Quadrature Mode 4 counts/cycle
Stop on Zero: (Configuration Bit 8)
This bit, when set, will hold the counter output at zero. When the counter counts
down to zero the counter will either count through zero or hold its output at zero
counts, until the Zero flag is cleared. When cleared the counter will continue to
count.
NOTE
The stop on zero function only applies to counts decrementing down
through zero.