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| author | Adam Izraelevitz | 2020-08-21 12:02:26 -0700 |
|---|---|---|
| committer | GitHub | 2020-08-21 19:02:26 +0000 |
| commit | 7edba2d10f980016462f917c6d21d64585ddfd6b (patch) | |
| tree | 3eb2a106b0e528b1ae8ed05b54200f828902de09 /docs/src/wiki-deprecated/troubleshooting.md | |
| parent | 70fd01d4b0ad18a87bc46558ff246254792aa9b8 (diff) | |
Added website docs and mdoc. (#1560)
* Added website docs and mdoc. Removed all warnings
* Updated README and added build to circle ci
* Added how to build documentation, deprecated wiki
* Fix copypasta
Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>
Diffstat (limited to 'docs/src/wiki-deprecated/troubleshooting.md')
| -rw-r--r-- | docs/src/wiki-deprecated/troubleshooting.md | 57 |
1 files changed, 57 insertions, 0 deletions
diff --git a/docs/src/wiki-deprecated/troubleshooting.md b/docs/src/wiki-deprecated/troubleshooting.md new file mode 100644 index 00000000..333adec4 --- /dev/null +++ b/docs/src/wiki-deprecated/troubleshooting.md @@ -0,0 +1,57 @@ +--- +layout: docs +title: "Troubleshooting" +section: "chisel3" +--- +This page is a starting point for recording common and not so common problems in developing with Chisel3. In particular, those situations where there is a work around that will keep you going. + +### `type mismatch` specifying width/value of a `UInt`/`SInt` + +*I have some old code that used to work correctly in chisel2 (and still does if I use the `import Chisel._` compatibility layer) +but causes a `type mismatch` error in straight chisel3:* + +```scala +class TestBlock extends Module { + val io = IO(new Bundle { + val output = Output(UInt(width=3)) + }) +} +``` +*produces* +```bash +type mismatch; +[error] found : Int(3) +[error] required: chisel3.internal.firrtl.Width +[error] val output = Output(UInt(width=3)) +``` + +The single argument, multi-function object/constructors from chisel2 have been removed from chisel3. +It was felt these were too prone to error and made it difficult to diagnose error conditions in chisel3 code. + +In chisel3, the single argument to the `UInt`/`SInt` object/constructor specifies the *width* and must be a `Width` type. +Although there are no automatic conversions from `Int` to `Width`, an `Int` may be converted to a `Width` by applying the `W` method to an `Int`. +In chisel3, the above code becomes: +```scala +class TestBlock extends Module { + val io = IO(new Bundle { + val output = Output(UInt(3.W)) + }) +} +``` +`UInt`/`SInt` literals may be created from an `Int` with the application of either the `U` or `S` method. + +```scala +UInt(42) +``` +in chisel2, becomes +```scala +42.U +``` +in chisel3 + +A literal with a specific width is created by calling the `U` or `S` method with a `W` argument. +Use: +```scala +1.S(8.W) +``` +to create an 8-bit wide (signed) literal with value 1. |
