6502.org

Posted: **Sun Jan 16, 2022 10:45 pm**

After many years of research and experiments I think it is time to present you the result - the 6502 simulator (or emulator) on the gate level - Breaks Debugger.

https://github.com/emu-russia/breaks/re ... s-debug-17

(If you're interested you can read the development history of previous versions there)

The Debugger consists of two parts - GUI in c# to display the internals of the processor and native code in c++ which contains the actual emulation of the processor. When you click on the "Step" button, the processor performs one half-cycle and the GUI shows you what's there. The debugger also includes a simple assembler that compiles a 64 Kbyte memory blob at once.

The data flow diagram for the lower part with slight modifications is taken from the dissection of 6502 by ttlworks. Thanks ttlworks!

It is possible to dump the internals as Markdown with pictures, for this you need to create a folder WikiMarkdown, where results will be stored.

An example of what results can be seen here: https://github.com/emu-russia/breaks/bl ... /ops/A2.md

Source code of the 6502 emulator here: https://github.com/emu-russia/breaks/tr ... /M6502Core

Posted: **Tue Jan 18, 2022 12:02 am**

Fixed the emulation of the tricky S register.

https://github.com/emu-russia/breaks/re ... s-debug-15

Posted: **Tue Jan 18, 2022 11:09 am**

It was a great joy to see how the 6502 uses S as a temporary during JSR!

Posted: **Wed Jan 19, 2022 4:29 pm**

https://github.com/emu-russia/breaks/re ... s-debug-16

All 6502 instructions are now executed correctly.

Posted: **Wed Jan 19, 2022 4:49 pm**

UnitTest Mode

To run the debugger in unit test mode, you need to create a JSON like this:

Code: Select all

json
{
	"CompileFromSource": true,
	"MemDumpInput": "mem.bin",
	"AsmSource": "Test.asm",
	"RamStart": "0",
	"RamSize": "0x800",
	"RomStart": "0xc000",
	"RomSize": "0x4000",
	"RunUntilBrk": true,
	"RunCycleAmount": true,
	"CycleMax": 10000,
	"DumpMem": true,
	"JsonResult": "res.json",
	"MemDumpOutput": "mem2.bin"
}

And run with parameter:

Code: Select all

BreaksDebugger Test.json

As input code, you can use 64 Kbytes memory dump (MemDumpInput) or assembly language source (AsmSource).

Simulator will run until it encounters instruction `BRK` (RunUntilBrk) or specified number of cycles (RunCycleAmount, CycleMax) (These are cycles, not half-cycles).

The output will be a memory dump after simulation (MemDumpOutput) and JSON with simulation results (JsonResult).

Posted: **Fri Jan 21, 2022 5:16 pm**

The M6502Core is tested in the Nintendulator:

https://github.com/emu-russia/breaks/re ... s-debug-17

Posted: **Fri Jan 21, 2022 6:19 pm**

Oh, do I take it you found a couple of bugs not spotted by Klaus Dormann's test?

Posted: **Tue Jan 25, 2022 11:43 am**

Thanks for the tip, I'll check them out too!

Posted: **Mon Feb 07, 2022 2:50 pm**

All functional tests of the 6502 by Klaus Dormann are successful.

I ran the unit test with these parameters:

Code: Select all

{
	"CompileFromSource": false,
	"MemDumpInput": "6502_functional_test.bin",
	"AsmSource": "Test.asm",
	"RamStart": "0",
	"RamSize": "0x8000",
	"RomStart": "0xc000",
	"RomSize": "0x4000",
	"RunUntilBrk": false,
	"RunCycleAmount": true,
	"CycleMax": 120000000,
	"RunUntilPC": true,
	"PC": "0x3469",
	"TraceMemOps": false,
	"TraceCLK": true,
	"DumpMem": true,
	"JsonResult": "res.json",
	"MemDumpOutput": "mem_out.bin"
}

The original image was slightly patched (RESET = 0x0400).

The state of the registers and the CLK on the output:

Code: Select all

{"A":"0xF0","X":"0x0E","Y":"0xFF","S":"0xFF","PC":"0x3469","C":1,"Z":0,"I":0,"D":0,"V":1,"N":1,"CLK":96241361}

6502.org

Breaks Debugger + 6502 Simulator on gate level

Breaks Debugger + 6502 Simulator on gate level

Re: Breaks Debugger + 6502 Simulator on gate level

Re: Breaks Debugger + 6502 Simulator on gate level

Re: Breaks Debugger + 6502 Simulator on gate level

Re: Breaks Debugger + 6502 Simulator on gate level

Re: Breaks Debugger + 6502 Simulator on gate level

Re: Breaks Debugger + 6502 Simulator on gate level

Re: Breaks Debugger + 6502 Simulator on gate level

Re: Breaks Debugger + 6502 Simulator on gate level