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[/] [zipcpu/] - Rev 71

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71 This contains a bunch of bug fixes. (A lot ...) For example, the pipeline
stall code has also seriously changed, to fixed the pipeline memory load/op
stage conflict, while maintaining no-stall operation for operands that don't
need an offset. This had a cascading effect, however, so that the multiply
could no longer complete in a single cycle. Therefore, the timing on the
multiplies was slowed down to two cycles from a single cycle. (It's the
only two-cycle ALU operation ...) The illegal instruction code has also been
fixed, so that illegal instructions no longer stalls the prefetch bus.
dgisselq 2470d 04h /zipcpu/
70 Updated the assembler support files, zopcodes in particular, to handle
the disassembly of the new very long instruction word codes.
dgisselq 2470d 04h /zipcpu/
69 This implements the "new Instruction Set" architecture for the Zip CPU. It's
a massive change set, that touches just about everything but probably not
enough of everything. Please see the spec.pdf for a description of this
new architecture.
dgisselq 2476d 09h /zipcpu/
68 Updated specification, includes well illustrated pipeline discussion. dgisselq 2511d 09h /zipcpu/
67 Includes timing diagrams in support of a very descriptive specification section. dgisselq 2511d 09h /zipcpu/
66 Adjusted the support for the DEBUG_SCOPE within these so that it can be
compiled in, or not, based upon an external build configuration file: cpudefs.v.
That allows me to make that file project specific, while the rest of the CPU
is shared among all projects.
dgisselq 2537d 09h /zipcpu/
65 Lots of logic simplifications to the core, in addition to better support for
illegal instruction detection and bus error detection. The biggest change
had to deal with pushing the debug write interface into the ALU write
processing path. This simplifies the logic of adjusting the PC and CC
registers primarily, but also any writes to other registers. It also delays
these register writes by a clock, but since the debug interface is already
ridiculously slow I doubt that matters any.
dgisselq 2537d 09h /zipcpu/
64 Shuffled some comments into here from elsewhere. dgisselq 2537d 09h /zipcpu/
63 Simplified bus interactions, and added support for detecting illegal
instructions (i.e. bus errors) in the pipefetch routine.
dgisselq 2537d 09h /zipcpu/
62 Simplified the subtraction logic, so the carry bit no longer depends on
a separate 32-bit operation but becomes part of the subtract operation.
dgisselq 2537d 09h /zipcpu/
61 Simplified the bus delay logic. Depends upon the stall line being irrelevant
outside of a bus cycle.
dgisselq 2537d 09h /zipcpu/
60 Fixed assembler processing of jump instructions, so that the new fast
return instruction can be used. The test file was modified to test
pipelined value passing within the CPU. That's where the value gets
(re)used before being stored back in the register file. As of this release,
all tests work.
dgisselq 2537d 09h /zipcpu/
59 Adjusted these library routines to use the new stack frame and calling
conventions.
dgisselq 2537d 09h /zipcpu/
58 Added a rudimentary profiling support to the simulator. dgisselq 2537d 09h /zipcpu/
57 Some bug fixes to the dhrystone benchmark, and some compile time defines for
the test bench processor. Of the most important note is the fix to detect
lockups on the debug/wishbone bus--that has been a real help in getting the
ZipCPU installed and the debugger working on the various boards I'm working
with. (i.e., it's helped me find and figure out why/when things haven't worked)
Of other note is the new 'G' key in the testbench code, to cause the test
bench to run without user interaction until the next keystroke. This is
very valuable in long programs, as it makes getting to/from breakpoints
easier (i.e. you don't have to wait as long, hit 'G', breathe, hit 'space'
and you're there).
dgisselq 2547d 11h /zipcpu/
56 Here's a bit of work in progress for getting the Zip CPU working on a XuLA2
board. Many changes include: the existence of a cpudefs.v file to control
what "options" are included in the ZipCPU build. This allows build control
to be separated from the project directory (one build for a XuLA2 board,
another for a Basys-3 development board). Other changes have made things
perhaps harder to read, but they get rid of warnings from XST.

A big change was the addition of the (* ram_style="distributed" *) comment
for the register set. This was necessary to keep XST from inferring a block
RAM and breaking the logic that was supposed to take place between a register
read and when it was used.
dgisselq 2547d 11h /zipcpu/
55 A test was added to double check whether carry following right shifts worked.
This was a necessary part of getting two cycle linear feedback shift register
operations working for a memory test on a XuLA2 board. With this, I can now
verify that such feedback registers work for pseudorandom number purposes.
dgisselq 2547d 12h /zipcpu/
54 This builds on the support for backslash character escapes in both single
and multicharacter expressions. Backslash character escapes are now
possible with quotations and backslashes, and the same code to interpret
the escapes is applied to both single and multicharacter sequences.
dgisselq 2547d 12h /zipcpu/
53 Updated the #include/#define directives to work properly for nested includes.
(They were supposed to work properly for nested includes before ... and didn't)
This fixes those bugs.
dgisselq 2547d 12h /zipcpu/
52 Added the capability to "see" character's encoded within a binary file,
by printing the character value(s) of each opcode (if they are printable)
on each line.
dgisselq 2547d 12h /zipcpu/

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