17 lines
936 B
Markdown
17 lines
936 B
Markdown
# 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._ |