Attention
This documentation is a work in progress. Expect to see errors and unfinished things.
freq_count
Description
Synthesizes to 86 slices at 312 MHz in XC3Sxxx-4 using XST-8.2i
(well, that’s just the unknown frequency input; max sysclk is 132 MHz)
Pinout
Parameters
Name |
Min |
Max |
Default |
Description |
|---|---|---|---|---|
glitch_thresh |
? |
? |
2 |
|
refcnt_width |
? |
? |
24 |
|
freq_width |
? |
? |
28 |
|
initv |
? |
? |
0 |
Ports
Signal |
Direction |
Description |
|---|---|---|
sysclk |
Input |
timespec 8.0 ns |
f_in |
Input |
unknown input |
frequency[freq_width-1:0] |
Output |
|
freq_strobe |
Output |
|
diff_stream[15:0] |
Output |
stream of last 4 4-bit counts of f_in |
diff_stream_strobe |
Output |
strobe at f_sysclk/4 |
glitch_catcher |
Output |
Implementation and use
The portable Verilog implementation can be found in freq_count Source File
Timing Diagram
A GTKWave-generated timing diagram is shown below:
