COUNTER - Up/Down pulse counter

Each counter block, when enabled, can count up/down with user-defined step value on the rising edge on input trigger. The counters can also be initialised to a user-defined START value.

Fields

Name	Type	Description
ENABLE	bit_mux	Halt on falling edge, reset and enable on rising
TRIG	bit_mux	Rising edge ticks the counter up/down by STEP
DIR	bit_mux	Up/Down direction (0 = Up, 1 = Down)
TRIG_EDGE	param enum	INP trigger edge 0 Rising 1 Falling 2 Either
OUT_MODE	param enum	Counter OUT update mode (on internal counter value change or on ENABLE falling edge) 0 On-Change 1 On-Disable
SET	param int	set current value of a counter
START	param int	Counter start value
STEP	param	Up/Down step value
MAX	param int	Rollover value
MIN	param int	Value to which counter should rollover to
CARRY	bit_out	Internal counter overflow status
OUT	pos_out	Current counter value

Counting pulses

The most common use of a counter block is when you would like to track the number of trigger edges received while enabled:

(Source code, png, hires.png, pdf)

The TRIG_EDGE field can be used to select the track on rising, falling, or both edges:

(Source code, png, hires.png, pdf)

You can also set the start value to be loaded on enable, and step up by a number other than one:

(Source code, png, hires.png, pdf)

You can also set the direction that a pulse should apply step, so it becomes an up/down counter. The direction is sampled on the same clock tick as the pulse edge:

(Source code, png, hires.png, pdf)

(Source code, png, hires.png, pdf)

When the OUT_MODE is set to On-Disable, the OUT output will only be changed to the internal counter value on ENABLE’s falling edge:

(Source code, png, hires.png, pdf)

Rollover

If the count goes higher than the max value for an int32 (2147483647) the CARRY output gets set high and the counter rolls. The CARRY output stays high for as long as the trigger input stays high.

(Source code, png, hires.png, pdf)

A similar thing happens for a negative overflow:

(Source code, png, hires.png, pdf)

When the OUT_MODE is set to On-Disable, the CARRY output will get set to high on ENABLE’s falling edge if any overflow produced while the counter was enabled:

(Source code, png, hires.png, pdf)