Programming the Gigatron

CPU

CPU instructions

gtemu.c

# 00 # 20 # 40 # 60 # 80 # a0 # c0 # e0 ---+-----------------------+---------------------------+---------------------------+---------------------------+---------------------------+---------------------------+--------------------------+--------------------------------- 00 # A = oper # A &= oper # A |= oper # A ^= oper # A += oper # A -= oper # RAM[oper] = oper # PC = (Y>>8)|oper 04 # A = oper # A &= oper # A |= oper # A ^= oper # A += oper # A -= oper # RAM[X] = oper # if (A < 0) PC = hi(PC)|oper 08 # A = oper # A &= oper # A |= oper # A ^= oper # A += oper # A -= oper # RAM[(Y>>8)|oper] = oper # if (A > 0) PC = hi(PC)|oper 0c # A = oper # A &= oper # A |= oper # A ^= oper # A += oper # A -= oper # RAM[(Y>>8)|X] = oper # if (A != 0) PC = hi(PC)|oper 10 # X = oper # X = A & oper # X = A | oper # X = A ^ oper # X = A + oper # X = A - oper # RAM[oper] = oper; X = A # if (A == 0) PC = hi(PC)|oper 14 # Y = oper # Y = A & oper # Y = A | oper # Y = A ^ oper # Y = A + oper # Y = A - oper # RAM[oper] = oper; Y = A # if (A <= 0) PC = hi(PC)|oper 18 # OUT = oper # OUT = A & oper # OUT = A | oper # OUT = A ^ oper # OUT = A + oper # OUT = A - oper # RAM[oper] = oper # if (A >= 0) PC = hi(PC)|oper 1c # OUT = oper; X++ # OUT = A & oper; X++ # OUT = A | oper; X++ # OUT = A ^ oper; X++ # OUT = A + oper; X++ # OUT = A - oper; X++ # RAM[(Y>>8)|X++] = oper # PC = hi(PC)|oper 01 # A = RAM[oper] # A &= RAM[oper] # A |= RAM[oper] # A ^= RAM[oper] # A += RAM[oper] # A -= RAM[oper] # RAM[oper] = undef # PC = (Y>>8)|RAM[oper] 05 # A = RAM[X] # A &= RAM[X] # A |= RAM[X] # A ^= RAM[X] # A += RAM[X] # A -= RAM[X] # RAM[X] = undef # if (A < 0) PC = hi(PC)|RAM[oper] 09 # A = RAM[(Y>>8)|oper] # A &= RAM[(Y>>8)|oper] # A |= RAM[(Y>>8)|oper] # A ^= RAM[(Y>>8)|oper] # A += RAM[(Y>>8)|oper] # A -= RAM[(Y>>8)|oper] # RAM[(Y>>8)|oper] = undef # if (A > 0) PC = hi(PC)|RAM[oper] 0d # A = RAM[(Y>>8)|X] # A &= RAM[(Y>>8)|X] # A |= RAM[(Y>>8)|X] # A ^= RAM[(Y>>8)|X] # A += RAM[(Y>>8)|X] # A -= RAM[(Y>>8)|X] # RAM[(Y>>8)|X] = undef # if (A != 0) PC = hi(PC)|RAM[oper] 11 # X = RAM[oper] # X = A & RAM[oper] # X = A | RAM[oper] # X = A ^ RAM[oper] # X = A + RAM[oper] # X = A - RAM[oper] # RAM[oper] = undef; X = A # if (A == 0) PC = hi(PC)|RAM[oper] 15 # Y = RAM[oper] # Y = A & RAM[oper] # Y = A | RAM[oper] # Y = A ^ RAM[oper] # Y = A + RAM[oper] # Y = A - RAM[oper] # RAM[oper] = undef; Y = A # if (A <= 0) PC = hi(PC)|RAM[oper] 19 # OUT = RAM[oper] # OUT = A & RAM[oper] # OUT = A | RAM[oper] # OUT = A ^ RAM[oper] # OUT = A + RAM[oper] # OUT = A - RAM[oper] # RAM[oper] = undef # if (A >= 0) PC = hi(PC)|RAM[oper] 1d # OUT = RAM[(Y>>8)|X++] # OUT = A & RAM[(Y>>8)|X++] # OUT = A | RAM[(Y>>8)|X++] # OUT = A ^ RAM[(Y>>8)|X++] # OUT = A + RAM[(Y>>8)|X++] # OUT = A - RAM[(Y>>8)|X++] # RAM[(Y>>8)|X++] = undef # PC = hi(PC)|RAM[oper] 02 # /*nop*/ # /*nop*/ # /*nop*/ # A = 0 # A *= 2 # A = 0 # RAM[oper] = A # PC = (Y>>8)|A 06 # /*nop*/ # /*nop*/ # /*nop*/ # A = 0 # A *= 2 # A = 0 # RAM[X] = A # if (A < 0) PC = hi(PC)|A 0a # /*nop*/ # /*nop*/ # /*nop*/ # A = 0 # A *= 2 # A = 0 # RAM[(Y>>8)|oper] = A # if (A > 0) PC = hi(PC)|A 0e # /*nop*/ # /*nop*/ # /*nop*/ # A = 0 # A *= 2 # A = 0 # RAM[(Y>>8)|X] = A # if (A != 0) PC = hi(PC)|A 12 # X = A # X = A # X = A # X = 0 # X = 2*A # X = 0 # RAM[oper] = A; X = A # if (A == 0) PC = hi(PC)|A 16 # Y = A # Y = A # Y = A # Y = 0 # Y = 2*A # Y = 0 # RAM[oper] = A; Y = A # if (A <= 0) PC = hi(PC)|A 1a # OUT = A # OUT = A # OUT = A # OUT = 0 # OUT = 2*A # OUT = 0 # RAM[oper] = A # if (A >= 0) PC = hi(PC)|A 1e # OUT = A; X++ # OUT = A; X++ # OUT = A; X++ # OUT = 0; X++ # OUT = 2*A; X++ # OUT = 0; X++ # RAM[(Y>>8)|X++] = A # PC = hi(PC)|A 03 # A = IN # A &= IN # A |= IN # A ^= IN # A += IN # A -= IN # RAM[oper] = IN # PC = (Y>>8)|IN 07 # A = IN # A &= IN # A |= IN # A ^= IN # A += IN # A -= IN # RAM[X] = IN # if (A < 0) PC = hi(PC)|IN 0b # A = IN # A &= IN # A |= IN # A ^= IN # A += IN # A -= IN # RAM[(Y>>8)|oper] = IN # if (A > 0) PC = hi(PC)|IN 0f # A = IN # A &= IN # A |= IN # A ^= IN # A += IN # A -= IN # RAM[(Y>>8)|X] = IN # if (A != 0) PC = hi(PC)|IN 13 # X = IN # X = A & IN # X = A | IN # X = A ^ IN # X = A + IN # X = A - IN # RAM[oper] = IN; X = A # if (A == 0) PC = hi(PC)|IN 17 # Y = IN # Y = A & IN # Y = A | IN # Y = A ^ IN # Y = A + IN # Y = A - IN # RAM[oper] = IN; Y = A # if (A <= 0) PC = hi(PC)|IN 1b # OUT = IN # OUT = A & IN # OUT = A | IN # OUT = A ^ IN # OUT = A + IN # OUT = A - IN # RAM[oper] = IN # if (A >= 0) PC = hi(PC)|IN 1f # OUT = IN; X++ # OUT = A & IN; X++ # OUT = A | IN; X++ # OUT = A ^ IN; X++ # OUT = A + IN; X++ # OUT = A - IN; X++ # RAM[(Y>>8)|X++] = IN # PC = hi(PC)|IN

Next, I wrote a progam to parse the theloop.asm file to discover which instructions are actually used. This resulted in the following output given below. In the first column the hexadecimal instruction number, in the second column the number of times the instruction is mentioned in the file, in the third column the pseudo-C code, and in the last column the mnemonic being used in the file. $00 stands for the operand.

inst # pseudo-C mnemonic ------------------------------------------------------------- 02 586: /*nop*/ // nop 00 54305: A = oper // ld $00 01 505: A = RAM[oper] // ld [$00] 03 1: A = IN // ld in 05 26: A = RAM[X] // ld [x] 09 2: A = RAM[(Y<<8)|oper] // ld [y,$00] 0d 32: A = RAM[(Y<<8)|X] // ld [y,x] 10 1: X = oper // ld $00,x 11 27: X = RAM[oper] // ld [$00],x 12 11: X = A // ld ac,x 14 326: Y = oper // ld $00,y 15 19: Y = RAM[oper] // ld [$00],y 16 2: Y = A // ld ac,y 18 14: OUT = oper // ld $00,out 19 6: OUT = RAM[oper] // ld [$00],out 20 33: A &= oper // anda $00 21 8: A &= RAM[oper] // anda [$00] 25 2: A &= RAM[X] // anda [x] 29 2: A &= RAM[(Y<<8)|oper] // anda [y,$00] 30 9: X = A & oper // anda $00,x 40 14: A |= oper // ora $00 41 17: A |= RAM[oper] // ora [$00] 45 3: A |= RAM[X] // ora [x] 50 6: X = A | oper // ora $00,x 5d 3: OUT = A | RAM[(Y<<8)|X++] // ora [y,x++],out 60 16: A ^= oper // xora $bf 61 11: A ^= RAM[oper] // xora [$00] 69 5: A ^= RAM[(Y<<8)|oper] // xora [y,$00] 80 402: A += oper // adda $00 81 28: A += RAM[oper] // adda [$00] 82 36: A *= 2 // adda ac 85 2: A += RAM[X] // adda [x] 89 6: A += RAM[(Y<<8)|oper] // adda [y,$00] 8d 4: A += RAM[(Y<<8)|X] // adda [y,x] 90 11: X = A + oper // adda $00,x 91 1: X = A + RAM[oper] // adda [$00],x 92 2: X = 2*A // adda ac,x 95 1: Y = A + RAM[oper] // adda [$00],y a0 28: A -= oper // suba $00 a1 3: A -= RAM[oper] // suba [$00] a5 5: A -= RAM[X] // suba [x] b0 3: X = A - oper // suba $00,x c0 4: RAM[oper] = oper // st $00,[$00] c2 662: RAM[oper] = A // st [$00] c3 2: RAM[oper] = IN // st in,[$00] c6 8: RAM[X] = A // st [x] ca 6: RAM[(Y<<8)|oper] = A // st [y,$00] ce 9: RAM[(Y<<8)|X] = A // st [y,x] d2 7: RAM[oper] = A; X = A // st [$00],x d6 8: RAM[oper] = A; Y = A // st [$00],y de 27: RAM[(Y<<8)|X++] = A // st [y,x++] dc 52: RAM[(Y<<8)|X++] = oper // st $00,[y,x++] e0 314: PC = (Y<<8)|oper // jmp y,$00 e1 2: PC = (Y<<8)|RAM[oper] // jmp y,[$00] e2 13: PC = (Y<<8)|A // jmp y,ac e4 3: if (A > 0) PC = hi(PC)|oper // bgt $00 e8 14: if (A < 0) PC = hi(PC)|oper // blt $00 ec 30: if (A != 0) PC = hi(PC)|oper // bne $00 f0 10: if (A == 0) PC = hi(PC)|oper // beq $00 f4 5: if (A >= 0) PC = hi(PC)|oper // bge $00 f8 2: if (A <= 0) PC = hi(PC)|oper // ble $00 fc 497: PC = hi(PC)|oper // bra $00 fd 2: PC = hi(PC)|RAM[oper] // bra [$00] fe 612: PC = hi(PC)|A // bra ac

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