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machxo2: Prepare README.md for first PR.

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William D. Jones 2021-02-10 19:27:34 -05:00 committed by gatecat
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machxo2/README.md
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# `nextpnr-machxo2` # `nextpnr-machxo2`
To be filled in w/ details later. _Experimental_ FOSS Place And Route backend for the Lattice MachXO2 family of
FPGAs. Fuzzing takes place as a subproject of [`prjtrellis`](https://github.com/YosysHQ/prjtrellis).
Known to work:
* Basic routing from pads to SLICEs and back!
* Basic packing of one type of FF and LUT into _half_ of a SLICE!
* Using the internal oscillator `OSCH` as a clock
* `LOGIC` SLICE mode
Things that probably work but are untested:
* Any non-3.3V I/O standard that doesn't use bank VREFs.
Things remaining to do include (but not limited to):
* More intelligent and efficient packing
* Global Routing (exists in database/sim models, `nextpnr-machxo2` doesn't use
it yet)
* Secondary High Fanout Nets
* Edge Clocks (clock pads work, but not routed to global routing yet)
* PLLs
* Synchronous Release Global Set/Reset Interface (`SGSR`)
* Embedded Function Block (`EFB`)
* All DDR-related functionality
* Bank VREFs
* Embedded Block RAM (`EBR`)
* `CCU2` and `DPRAM` SLICE modes
## Quick Start ## Quick Start
@ -19,7 +46,9 @@ python3-setuptools python3-serial
### Installation ### Installation
Use an empty directory to hold all the cloned repositories. Use an empty directory to hold all the cloned repositories. Upstream repos
can be used as well (e.g. [`YosysHQ/prjtrellis`](https://github.com/YosysHQ/prjtrellis),
etc.).
``` ```
git clone git@github.com:cr1901/prjtrellis.git git clone git@github.com:cr1901/prjtrellis.git
@ -56,6 +85,9 @@ cmake . -DARCH=machxo2 -DBUILD_GUI=OFF -DTRELLIS_INSTALL_PREFIX=/usr -DBUILD_PY
make make
``` ```
Although uncommon, the `facade` and `machxo2` branches of the above repos are
occassionally rebased; use `git pull -f` if necessary.
### Demo ### Demo
If you have a [TinyFPGA Ax2](https://store.tinyfpga.com/products/tinyfpga-a2) board If you have a [TinyFPGA Ax2](https://store.tinyfpga.com/products/tinyfpga-a2) board
@ -65,9 +97,9 @@ MachXO2; the gateware will flash the LED!
``` ```
cd machxo2/examples/ cd machxo2/examples/
sh demo.sh sh demo.sh tinyfpga
``` ```
The `tinyfpga.v` code used in `demo.sh` is slightly modified from the The `tinyfpga.v` code used in `demo.sh` is slightly modified from the
[user's guide](https://tinyfpga.com/a-series-guide.html) to accommodate [user's guide](https://tinyfpga.com/a-series-guide.html) to accommodate
`(* LOC = "pin" *)` constraints. `(* LOC = "pin" *)` constraints and the built-in user LED.