diff options
Diffstat (limited to 'docs')
| -rw-r--r-- | docs/ice40.md | 17 |
1 files changed, 17 insertions, 0 deletions
diff --git a/docs/ice40.md b/docs/ice40.md new file mode 100644 index 00000000..f142f078 --- /dev/null +++ b/docs/ice40.md @@ -0,0 +1,17 @@ +# iCE40 Architecture Documentation + +## PCF format reference + +PCF files contain physical constraints and are specified using the `--pcf` argument. Each (non blank) line contains a command; lines beginning with `#` are comments. + +Two commands are supported: `set_io` and `set_frequency`. + + set_io [-nowarn] [-pullup yes|no] [-pullup_resistor 3P3K|6P8K|10K|100K] port pin + +Constrains named port `port` to package pin `pin`. `-nowarn` disables the warning if `port` does not exist. `-pullup yes` can be used to enable the built in pullup for all iCE40 devices. `-pullup_resistor` sets the pullup strength, and is available on iCE40 UltraPlus only. + + set_frequency net frequency + +Adds a clock constraint to a named net (any alias for the net can be used). `frequency` is in MHz. + +_Note that this is a non-standard extension, not supported by the vendor toolchain. It allows specifying clock constraints without needing the Python API._
\ No newline at end of file |