This also changes `decoder` a bit: when an enum is used as a decoder,
it is converted to a `Format.Enum` instead. The original enum is still
stored on the `decoder` attribute, so that it can be propagated
on `Signal.like`.
This includes a few minor code changes:
- Removing redundant `lib.memory.Memory.Init = hdl.MemoryData.Init`
re-export;
- Renaming `FrozenError` to `FrozenMemory` and moving it to `.hdl`;
- Marking `ReadPort` and `WritePort` as `@final`.
This check was originally added out of abundance of caution, but since
then it was observed that reset-less-ness is purely an implementation
detail (see #1220), and furthermore it interferes with adaptation of
`FIFOInterface`` signals (where `[rw]_data` are reset-less) for RFC 61.
These accessors used to be necessary (in addition to `.shape()`) while
the AST nodes were mutable. However, after commit 2bf1b4da that made
AST nodes immutable, there is no technical requirement to keep them
around. Additionally:
- `len(value)` is shorter than `value.width` and works with any `value`
- `value.shape().signed` is longer than `value.signed` but works with
any `value`
* Given a private name `$\d+` in RTLIL (as they are not named in the IR)
* Not automatically added to VCD files (as they are not named in the IR)
* Cannot be traced to a VCD (as they have no name to put in the file)
* Cannot be used with an unnamed top-level port (as there is no name)
If delta cycles are expanded (i.e. if the `fs_per_delta` argument to
`Simulator.write_vcd` is not zero), then create a string typed variable
for each testbench in the simulation, which reflects the current
command being executed by that testbench. To make all commands visible,
insert a (visual) delta cycle after each executed command, and ensure
that there is a change/crossing point in the waveform display each time
a command is executed, even if several identical ones in a row.
If delta cycles are not expanded, the behavior is unchanged.
This commit adds an option `fs_per_delta=` to `Simulator.write_vcd()`.
Specifying a positive integer value for it causes the simulator to
offset value change times by that many femtoseconds for each delta
cycle after the last timeline advancement.
This option is only suitable for debugging. If the timeline is advanced
by less than the combined duration of expanded delta cycles, an error
similar to the following will be raised:
vcd.writer.VCDPhaseError: Out of order timestamp: 62490
Typically `fs_per_delta=1` is best, since it allows thousands of delta
cycles to be expanded without risking a VCD phase error, but bigger
values can be used for an exaggerated visual effect.
Also, the VCD writer is changed to use 1 fs as the timebase instead of
1 ps. This change is largely invisible to designers, resulting only in
slightly larger VCD files due to longer timestamps.
Since the `fs_per_delta=` option is per VCD writer, it is possible to
simultaneously dump two VCDs, one with and one without delta cycle
expansion:
with sim.write_vcd("sim.vcd"), sim.write_vcd("sim.d.vcd", fs_per_delta=1):
sim.run()
