diff options
| -rw-r--r-- | LINKS | 8 | ||||
| -rw-r--r-- | doc/MINIMAL.6502 | 49 | ||||
| -rw-r--r-- | emu/6522.h | 1 | ||||
| -rw-r--r-- | emu/emul.c | 19 |
4 files changed, 77 insertions, 0 deletions
@@ -120,6 +120,10 @@ https://github.com/davepoo/6502Emulator https://github.com/spacerace/6502 https://www.masswerk.at/products.php +other minimal PC projects +https://github.com/slu4coder/Minimalistic-8-Bit-CPU +https://www.youtube.com/channel/UCXYQcMpUBT3aaQKfmAVJNow + other emulators: https://github.com/pdewacht/oberon-risc-emu (RISC-5 Wirth Emulator, as inspiration) @@ -149,3 +153,7 @@ https://github.com/vndmtrx/check-cmake-example cmake: https://samthursfield.wordpress.com/2015/11/21/cmake-dependencies-between-targets-and-files-and-custom-commands/ + +languages for 6502: +https://dwheeler.com/6502/ +http://cowlark.com/cowgol/ diff --git a/doc/MINIMAL.6502 b/doc/MINIMAL.6502 new file mode 100644 index 0000000..ae2044d --- /dev/null +++ b/doc/MINIMAL.6502 @@ -0,0 +1,49 @@ +Immediate ADI +Absolute ADA +Relative ADR + +little endian + +lda +sta +clr +neg +inc +dec +cpi +adc +sbc +jmp +jsr + +nop +clc +sec +not +lsl +rol +lsr +ror +asr +rts +phs +pls + + +rel +word at abs adr +SP+rel + +bran + +no interrups, but win/out + +0x7fff 255 byte stack (instead of 0x100 to 0x1ff on 6502) + +sts/lds store relative to stack +function calls with parameters + +XXW codes, acting on 16-bit words + +WIN, OUT as shortcurs, not really necessary +relative addressing for jumps would help to write relocatable code by hand @@ -38,6 +38,7 @@ typedef struct via_6522_t uint8_t ddrb; uint8_t pcr; uint8_t ier; + uint8_t ifr; bool debug; @@ -81,6 +81,7 @@ static void print_help( void ) "(f) fini (continue to next rts)\n" "(c) for continue running\n" "(b) break to single stepping\n" + "(d) toggle debug output\n" "(+) speed up\n" "(-) speed down\n" "(p) push the button\n" @@ -124,6 +125,19 @@ void emul_run( emul_t *emul, int nof_steps ) case SDLK_s: cpu_6502_run_steps( emul->cpu, 1 ); break; + case SDLK_d: + if( emul->speed < 250 ) { + emul->debug = !emul->debug; + fprintf( stderr, "debug mode is %s\n", ( emul->debug) ? "on" : "off" ); + if( emul->debug ) { + emul->cpu->debug_flags |= DEBUG_STATUS; + } else { + emul->cpu->debug_flags &= ~DEBUG_STATUS; + } + } else { + fprintf( stderr, "enabling debug mode now not possible, CPU is too fast!\n" ); + } + break; case SDLK_EQUALS: case SDLK_KP_EQUALS: case SDLK_PLUS: @@ -133,6 +147,11 @@ void emul_run( emul_t *emul, int nof_steps ) emul->speed = CPU_FREQUENCY; } fprintf( stderr, "CPU speed is %1.6f MHz now\n", ( (double)emul->speed / 1000000 ) ); + if( emul->speed > 250 ) { + emul->debug = false; + emul->cpu->debug_flags &= ~DEBUG_STATUS;; + fprintf( stderr, "disabling debug mode because the CPU is too fast now!\n" ); + } break; case SDLK_MINUS: case SDLK_KP_MINUS: |