Spectrum 1746sc-CTR4, Owner'S Manual, Page: 32 / 66

32
SLC 500 ™ 50 KHz Counter / Flowmeter Module
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 2
nd
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 Mode Mode Mode Mode Channels Channels Channels Channels Channels Bits Bits Bits Bits Bits Function Function Function Function 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.