exampleProgram.txt

; Example Z80 assembler program to perform Euclid's algorithm
; This isn't written for any actual assembler; it's just my
; notes for me to hand assemble.

; Pseudocode from Wikipedia:
; function gcd(a, c)
;    while a != c
;        if a > c
;           a := a − c
;        else
;           c := c − a
;    return a

; Second version, hand assembled:

ADDR OP HIGH LOW  DISASSEMBLY
0000 3E 0011 1110 LD A, #N
0001 36 0011 0110 #52
0002 06 0000 0110 LD B, #N
0003 4E 0100 1110 #78

loop:
0004 B8 1011 1000 CP B
0005 38 0011 1000 JP C +N
0006 05 0000 0101 #6  (b_gt_a)
0007 28 0010 1000 JP Z +N
 
0008 0A 0000 1010 #10 (done)
0009 90 1001 0000 SUB A, B
0010 18 0001 1000 JP N+2
0011 F8 1111 1000 #-8 (loop)
b_gt_a:
0012 4F 0100 1111 LD C, A
0013 78 0111 1000 LD A, B
0014 91 1001 0001 SUB A, C
0015 47 0100 0111 LD B, A

0016 79 0111 1001 LD A, C
0017 18 0001 1000 JP N+2
0018 F1 1111 0001 #-10 (loop)
done:
0019 32 0011 0010 LD (NN), A

0020 80 1000 0000 #0x80
0021 00 0000 0000 #0x00
0022 18 0001 1000 JP N+2
0023 FB 1111 1011 #-4 (done)


# JP C test:

ADDR OP HIGH LOW  DISASSEMBLY
0000 3E 0011 1110 LD A, #N
0001 36 0011 0110 #52
0002 06 0000 0110 LD B, #N
0003 4E 0100 1110 #78

loop:
0004 B8 1011 1000 CP B
0005 38 0011 1000 JP C +N
0006    1111 1110 -1 > #0

This should should execute in a loop and not escape.
Yep, works

So the negative test:

ADDR OP HIGH LOW  DISASSEMBLY
0000 3E 0011 1110 LD A, #N
0001 4E 0100 1110 #78
0002 06 0000 0110 LD B, #N
0003 36 0011 0110 #52

loop:
0004 B8 1011 1000 CP B
0005 38 0011 1000 JP C +N
0006 0000 1000 -1 > #0
0007 0000 0000 NOP
0008 0000 0000 NOP

This should execute all the NOPs and not jump to 0009... TEst passes.

# JP Z test:

ADDR OP HIGH LOW  DISASSEMBLY
0000 3E 0011 1110 LD A, #N
0001 36 0011 0110 #78
0002 06 0000 0110 LD B, #N
0003 4E 0100 1110 #78

loop:
0004 B8 1011 1000 CP B
0005 38 0010 1000 JP Z +N
0006    1111 1110 -1 > #0

This should sit in a loop and never escape.
Yep, works