Dseg at 0x10
    aa equ r7
    bb equ r6
    cc equ r5
    ddd equ r4
    ii equ r3

    cseg at 0x0
jmp start

compare:
    clr c
    xrl a, #0x80 ; s.bb^1.00 inversion sign
    mov r0, a
    mov a, b
    xrl a, #0x80 ; s.aa^1.00 inversion sign
    subb a, r0 ; s.dd - s.aa
    ret

start:
    mov P0, #0
    mov ii, #0
    mov a, ii

loop:
    mov a, P1
    add a, ACC
    mov P1, a

; aa = a & 8
    mov a, ii
    anl a, #8
    mov aa, a
; bb = a & 4
    mov a, ii
    anl a, #4
    mov bb, a
; cc = a & 2
    mov a, ii
    anl a, #2
    mov cc, a
; dd = a - 4
    ;clr cc
    mov a, ii
    subb a, #4
    mov ddd, a

; (bb > cc)
    mov a, bb
    mov b, cc
    call compare
    jnc M1 ; if(bb>cc) goto M1

; (bb > cc) & (dd < bb)
    mov a, bb
    mov b, ddd
    call compare
    jnc M1 ; if (bb > dd) goto M1
    jmp M2

; (aa != dd)
M1:
    mov a, aa
    subb a, ddd
    jnz M2
    jmp M3

M2:
    mov r1, #0x01
    sjmp M4
M3:
    mov r1, #0x00 ; S=0
M4:
    mov a, P1
    orl a, r1 ; S=1
    mov P1, a

    inc ii
    mov a, ii
    cjne a, #0x08, loop
    mov P0, P1
    jmp $
end