901 PulseMon8
901 : PulseMon8
- Author: Gurtej Randhawa
- Description: 8-bit pulse monitor with edge detection and compare-match logic.
- GitHub repository
- Open in 3D viewer
- Open in Tiny Tapeout Explorer
- Clock: 0 Hz
How it works
PulseMon8 is an 8-bit pulse monitor that counts rising edges on an external input signal. The signal is sampled using the Tiny Tapeout clock, and a pulse is detected when the signal changes from low to high. Pulse detection also asserts the edge_detect output for one clock cycle.
The current count is displayed on uo_out[7:0]. Counting can be enabled or disabled using the enable input, and the count can be cleared using the clear input.
You can provide an 8-bit comparison value through ui_in[7:0]. When the current count is equal to this value, the match_status output is asserted. Since match_status directly compares the two values, it is also asserted when both the count and comparison value are zero.
The freeze_on_match input can be used to automatically stop the counter when a pulse causes the count to reach the comparison value. Once frozen, the freeze_status output remains asserted and additional pulses are ignored until the design is cleared or reset.
The overflow output is asserted when the counter increments past 255 and wraps back to zero. This flag remains asserted until the design is cleared or reset.
How to test
For a basic hardware test, first reset the design or set clear (uio_in[6]) high for one clock cycle. Set enable (uio_in[5]) high and keep freeze_on_match (uio_in[7]) low.
Generate a pulse by changing signal (uio_in[4]) from low to high. Since the input is sampled using the project clock, hold both the low and high levels for at least one clock cycle. Each rising edge should increase the count on uo_out[7:0] by one. Falling edges should not affect the count.
For example:
- Clear the design using
uio_in[6]. - Set
enable(uio_in[5]) high. - Apply three rising edges to
signal(uio_in[4]). - Confirm that
uo_out[7:0]displays3.
To test comparison and freezing:
- Clear the design.
- Set
compare_value(ui_in[7:0]) to3. - Set
enable(uio_in[5]) high. - Set
freeze_on_match(uio_in[7]) high. - Apply three rising edges to
signal(uio_in[4]). - Confirm that the count on
uo_out[7:0]stops at3. - Confirm that
match_status(uio_out[2]) andfreeze_status(uio_out[3]) are high. - Apply more pulses and confirm that the count remains unchanged.
- Assert
clear(uio_in[6]) and confirm that counting can begin again.
match_status is also high when both the count and comparison value are zero.
To test overflow, keep freeze_on_match (uio_in[7]) low and apply enough rising edges for the counter to wrap from 255 back to 0. overflow (uio_out[1]) should go high when the counter wraps and remain high until the design is cleared or reset.
External hardware
No custom external hardware is required.
The project can be tested using a Tiny Tapeout demoboard. The board controls can be used to set compare_value, enable, clear, and freeze_on_match. The pulse input can be driven using a switch, push button, microcontroller, function generator, or another digital signal source.
The current count can be observed on uo_out[7:0], while the status signals can be viewed using the demoboard outputs, LEDs, or a logic analyzer.
A mechanical push button may bounce and produce multiple rising edges from a single press. For more controlled testing, use a debounced button or another clean digital pulse source.
IO
| # | Input | Output | Bidirectional |
|---|---|---|---|
| 0 | compare_value[0] | count[0] | edge_detect |
| 1 | compare_value[1] | count[1] | overflow |
| 2 | compare_value[2] | count[2] | match_status |
| 3 | compare_value[3] | count[3] | freeze_status |
| 4 | compare_value[4] | count[4] | signal_in |
| 5 | compare_value[5] | count[5] | enable |
| 6 | compare_value[6] | count[6] | clear |
| 7 | compare_value[7] | count[7] | freeze_on_match |