Doing this in Chisel leads to non-determinism due to shitty
Verilog ordering semantis. Using an '=' ensures that all of
the clock posedges fire before concurrent register updates.
See "Gotcha 29: Sequential logic that requires blocking assignments"
in "Verilog and SystemVerilog Gotchas" by Stuart Sutherland, Don Mills.
If user compiles without +define+DEBUG but then requests +vcdfile at
simulation time, that request would be silently ignored. This changes
it to a fatal error.
It's good philosophy to treat plusargs like +vcdfile as commands, not
suggestions, and die immediately if they cannot be honored, instead of
silently ignoring them. Otherwise the user sits through the entire
simulation and then is left scratching his head wondering where his
waveforms are.
This fixes the following compile warnings and simulation errors:
Compile-time warnings:
$vcdplusfile(vcdplusfile);
|
ncelab: *W,MISSYST (/home/scottj/rocket-chip/vsrc/TestDriver.v,42|17): Unrecognized system task or function: $vcdplusfile (did not match built-in or user-defined names) [2.7.4(IEEE Std 1364-2001)].
$vcdpluson(0);
|
ncelab: *W,MISSYST (/home/scottj/rocket-chip/vsrc/TestDriver.v,43|15): Unrecognized system task or function: $vcdpluson (did not match built-in or user-defined names) [2.7.4(IEEE Std 1364-2001)].
$vcdplusmemon(0);
|
ncelab: *W,MISSYST (/home/scottj/rocket-chip/vsrc/TestDriver.v,44|18): Unrecognized system task or function: $vcdplusmemon (did not match built-in or user-defined names) [2.7.4(IEEE Std 1364-2001)].
`VCDPLUSCLOSE
|
ncelab: *W,MISSYST (/home/scottj/rocket-chip/vsrc/TestDriver.v,89|20): Unrecognized system task or function: $vcdplusclose (did not match built-in or user-defined names) [2.7.4(IEEE Std 1364-2001)].
Which then become simulation-time errors:
$vcdplusfile(vcdplusfile);
|
ncsim: *E,MSSYSTF (/home/scottj/rocket-chip/vsrc/TestDriver.v,42|17): User Defined system task or function ($vcdplusfile) registered during elaboration and used within the simulation has not been registered during simulation.
$vcdpluson(0);
|
ncsim: *E,MSSYSTF (/home/scottj/rocket-chip/vsrc/TestDriver.v,43|15): User Defined system task or function ($vcdpluson) registered during elaboration and used within the simulation has not been registered during simulation.
$vcdplusmemon(0);
|
ncsim: *E,MSSYSTF (/home/scottj/rocket-chip/vsrc/TestDriver.v,44|18): User Defined system task or function ($vcdplusmemon) registered during elaboration and used within the simulation has not been registered during simulation.
`VCDPLUSCLOSE
|
ncsim: *E,MSSYSTF (/home/scottj/rocket-chip/vsrc/TestDriver.v,89|20): User Defined system task or function ($vcdplusclose) registered during elaboration and used within the simulation has not been registered during simulation.
`VCDPLUSCLOSE
|
ncsim: *E,MSSYSTF (/home/scottj/rocket-chip/vsrc/TestDriver.v,97|20): User Defined system task or function ($vcdplusclose) registered during elaboration and used within the simulation has not been registered during simulation.
The SystemVerilog LRM (IEEE 1800-2012) clause 20.15.1 ($random
function) says: "The seed argument shall be an integral variable."
This fixes the following compile warning:
rand_value = $random($urandom);
|
ncelab: *W,WRNOTL (/home/scottj/rocket-chip/vsrc/TestDriver.v,34|23): Argument to out parameter is not a legal lvalue.
* debug: Clean up Debug TransportModule synchronizer
With async reset async queues, I feel its safe/cleaner
to remove the one-off "AsyncMailbox verilog black-box
and use the common primitive.
I also added some comments about correct usage of this
block. Probably the 'TRST' signal should be renamed
to make it less confusing, as it requires some processing
of the real JTAG 'TRST' signal.
* util: Do Set/Reset Async Registers more properly
The way BlackBox "init" registers were coded before was
not really kosher verilog for most synthesis tools.
Also, the enable logic wasn't really pushed down into the flop.
This change is more explicit about set/reset flops,
again this is only a 'temporary' problem that would go away
with parameterizable blackboxes (or general async reset support).
* Tabs, not spaces, in Makefiles
* util: Fix typos in Async BB Reg Comments
