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| author | Jack Koenig | 2021-02-04 10:07:56 -0800 |
|---|---|---|
| committer | GitHub | 2021-02-04 10:07:56 -0800 |
| commit | 8fa46071c382b6fdecba86a9bab729526fa4fbe2 (patch) | |
| tree | 41123124a8f27ec482693527c5140a8771b8881c /docs/src/wiki-deprecated/experimental-features.md | |
| parent | f45216effc573d33d4aa4e525cff955ab332efbd (diff) | |
Minor docs improvements (#1774)
* Fix some botched formatting (replace ```mdoc scala with ```scala mdoc)
* Replace some unnecessary uses of triple backticks with single
backticks
* Move appendix docs from wiki-deprecated/ to appendix/
* This will require an update on the website as well
* Update Bundle literal docs
Diffstat (limited to 'docs/src/wiki-deprecated/experimental-features.md')
| -rw-r--r-- | docs/src/wiki-deprecated/experimental-features.md | 119 |
1 files changed, 0 insertions, 119 deletions
diff --git a/docs/src/wiki-deprecated/experimental-features.md b/docs/src/wiki-deprecated/experimental-features.md deleted file mode 100644 index d36b2946..00000000 --- a/docs/src/wiki-deprecated/experimental-features.md +++ /dev/null @@ -1,119 +0,0 @@ ---- -layout: docs -title: "Experimental Features" -section: "chisel3" ---- - -Chisel has a number of new features that are worth checking out. This page is an informal list of these features and projects. - -### FixedPoint -FixedPoint numbers are basic *Data* type along side of UInt, SInt, etc. Most common math and logic operations -are supported. Chisel allows both the width and binary point to be inferred by the Firrtl compiler which can simplify -circuit descriptions. See [FixedPointSpec](https://github.com/freechipsproject/chisel3/tree/master/src/test/scala/chiselTests/FixedPointSpec.scala) - -### Module Variants -The standard Chisel *Module* requires a ```val io = IO(...)```, the experimental package introduces several -new ways of defining Modules -- BaseModule: no contents, instantiable -- BlackBox extends BaseModule -- UserDefinedModule extends BaseModule: this module can contain Chisel RTL. No default clock or reset lines. No default IO. - User should be able to specify non-io ports, ideally multiple of them. -- ImplicitModule extends UserModule: has clock, reset, and io, essentially current Chisel Module. -- RawModule: will be the user-facing version of UserDefinedModule -- Module: type-aliases to ImplicitModule, the user-facing version of ImplicitModule. - -### Bundle Literals - -Chisel 3.2 introduces an experimental mechanism for Bundle literals in #820, but this feature is largely incomplete and not ready for user code yet. The following is provided as documentation for library writers who want to take a stab at using this mechanism for their library's bundles. - -```mdoc scala -class MyBundle extends Bundle { - val a = UInt(8.W) - val b = Bool() - - // Bundle literal constructor code, which will be auto-generated using macro annotations in - // the future. - import chisel3.core.BundleLitBinding - import chisel3.internal.firrtl.{ULit, Width} - - // Full bundle literal constructor - def Lit(aVal: UInt, bVal: Bool): MyBundle = { - val clone = cloneType - clone.selfBind(BundleLitBinding(Map( - clone.a -> litArgOfBits(aVal), - clone.b -> litArgOfBits(bVal) - ))) - clone - } - - // Partial bundle literal constructor - def Lit(aVal: UInt): MyBundle = { - val clone = cloneType - clone.selfBind(BundleLitBinding(Map( - clone.a -> litArgOfBits(aVal) - ))) - clone - } -} -``` - -Example usage: - -```scala -val outsideBundleLit = (new MyBundle).Lit(42.U, true.B) -``` - -### Interval Type - -**Intervals** are a new experimental numeric type that comprises UInt, SInt and FixedPoint numbers. -It augments these types with range information, i.e. upper and lower numeric bounds. -This information can be used to exercise tighter programmatic control over the ultimate widths of -signals in the final circuit. The **Firrtl** compiler can infer this range information based on -operations and earlier values in the circuit. Intervals support all the ordinary bit and arithmetic operations -associated with UInt, SInt, and FixedPoint and adds the following methods for manipulating the range of -a **source** Interval with the IntervalRange of **target** Interval - -#### Clip -- Fit the value **source** into the IntervalRange of **target**, saturate if out of bounds -The clip method applied to an interval creates a new interval based on the argument to clip, -and constructs the necessary hardware so that the source Interval's value will be mapped into the new Interval. -Values that are outside the result range will be pegged to either maximum or minimum of result range as appropriate. - -> Generates necessary hardware to clip values, values greater than range are set to range.high, values lower than range are set to range min. - -#### Wrap -- Fit the value **source** into the IntervalRange of **target**, wrapping around if out of bounds -The wrap method applied to an interval creates a new interval based on the argument to wrap, -and constructs the necessary -hardware so that the source Interval's value will be mapped into the new Interval. -Values that are outside the result range will be wrapped until they fall within the result range. - -> Generates necessary hardware to wrap values, values greater than range are set to range.high, values lower than range are set to range min. - -> Does not handle out of range values that are less than half the minimum or greater than twice maximum - -#### Squeeze -- Fit the value **source** into the smallest IntervalRange based on source and target. -The squeeze method applied to an interval creates a new interval based on the argument to clip, the two ranges must overlap -behavior of squeeze with inputs outside of the produced range is undefined. - -> Generates no hardware, strictly a sizing operation - -##### Range combinations - -| Condition | A.clip(B) | A.wrap(B) | A.squeeze(B) | -| --------- | --------------- | --------------- | --------------- | -| A === B | max(Alo, Blo), min(Ahi, Bhi) | max(Alo, Blo), min(Ahi, Bhi) | max(Alo, Blo), min(Ahi, Bhi) | -| A contains B | max(Alo, Blo), min(Ahi, Bhi) | max(Alo, Blo), min(Ahi, Bhi) | max(Alo, Blo), min(Ahi, Bhi) | -| B contains A | max(Alo, Blo), min(Ahi, Bhi) | max(Alo, Blo), min(Ahi, Bhi) | max(Alo, Blo), min(Ahi, Bhi) | -| A min < B min, A max in B | max(Alo, Blo), min(Ahi, Bhi) | max(Alo, Blo), min(Ahi, Bhi) | max(Alo, Blo), min(Ahi, Bhi) | -| A min in B, A max > B max | max(Alo, Blo), min(Ahi, Bhi) | max(Alo, Blo), min(Ahi, Bhi) | max(Alo, Blo), min(Ahi, Bhi) | -| A strictly less than B | error | error | error | -| A strictly greater than B | error | error | error | - - -#### Applying binary point operators to an Interval - -Consider a Interval with a binary point of 3: aaa.bbb - -| operation | after operation | binary point | lower | upper | meaning | -| --------- | --------------- | ------------ | ----- | ----- | ------- | -| setBinaryPoint(2) | aaa.bb | 2 | X | X | set the precision | -| shiftLeftBinaryPoint(2) | a.aabbb | 5 | X | X | increase the precision | -| shiftRighBinaryPoint(2) | aaaa.b | 1 | X | X | reduce the precision | |
