jc      ret
        mov     dx,     -1
        push    dx                      ;stack position marker
C1:     mov     dl,     al
        call    ValCh                   ;returns hex number in dx
        jc      A1                      ;no more numbers. return
        push    dx
        lodsb
        jmp     short   C1
;---------------------------------------
AddNum: xor     ax,     ax              ;add up nibbles
        xor     cx,     cx              ;shl index
C2:     pop     dx
        cmp     dx,     -1              ;stack marker
        je      A2                      ;no more numbers. ret
        cmp     cl,     0               ;avoid looping error while "shl"ing
        je      C4
        push    cx
        push    ax
        mov     ax,     4               ;keep ah zero
        mul     cl
        mov     cl,     al
C3:     shl     dx,     1               ;keep it 8086 code
        loop    C3
        pop     ax
        pop     cx
C4:     add     ax,     dx
        inc     cx
        cmp     cx,     5               ;only 4 nipples to a customer
        jb      C2
;---------------------------------------
Err2:   pop     dx                      ;error. reset stack
        cmp     dx,     -1              ;stack marker
        jne     Err2
        stc
        ret
;-------------------------------------------------------------------------
; ValCh         Convert ASCII digit char to binary value
;---------------------------------------------------------------
; Input:
;       dl = ASCII digit '0'..'9'; 'A'..'F'
;      ; bx = base (2=binary, 10=decimal, 16=hexadecimal)
; Output:
;       cf = 0: dx = equivalent binary value
;       cf = 1: bad char for this number base (dx is meaningless)
; Registers:
;       dx
;---------------------------------------------------------------
ValCh proc
        cmp     dl, ':'         ;(as used here)
        je      V2
        cmp     dl, '9'         ; Check for possible hex digit
        jbe     V1              ; Probably '0'..'9', jump
        cmp     dl, 'F'
        jbe     V0
        xor     dl, 20h         ; assure upper case
V0:     sub     dl, 7           ; Adjust hex digit to 3A..3F range
V1:
        sub     dl, '0'         ; Convert ASCII to decimal
        test    dl, 0f0h        ; Check 4 msbs (sets cf=0) 11110000b
        jnz     V2              ; Jump if error (not digit or A-F)
        xor     dh, dh          ; Convert byte in dl to word in dx
       ; cmp     dx, bx          ; Compare to number base (cf=1 if ok)
        cmp     dx, 10h         ;base 16 (hardwired)
V2:
        cmc                     ; Complement cf to set/reset err flag
        ret                     ; Return to caller
ValCh endp
;--------------------------------------------------------------------
Hlp db 13,10,'PeekPoke v1 3-97 by Barry_Block@p42.f901.n280.z2.fidonet.org'
    db 13,10,10,'Usage: PeekPoke [seg:offset] [?,=] [b,w,d] {hex pair}'
    db 13,10,9,'segment:offset in hexidecmal'
    db 13,10,9,'? (peek), = (poke)'
    db 13,10,9,'b (byte), w (word), d (doubleword)'
    db 13,10,9,'{If used, hex data to poke, upper & lower nibble.}'
    db 13,10,10,'Examples:'
    db 13,10,9,'PeekPoke 40:0 ? w',9,9,'(show com1 address)'
    db 13,10,9,'PeekPoke 40:8 = d 78027803',9,'(exchange lpt1/lpt2)'
    db 13,10,9,'PeekPoke B800:0 = w 010e',9,'(note the leading 0!)'
    db 13,10,9,'(put a yellow face at the top left of a mode 3 screen)'
crlf db 13,10,36
data segment
org 1024+256
opt     db      ?
siz     dw      ?
oset    dw      ?
_seg    dw      ?
pok     db      ?
;end of file
--- Terminate 4.00/Pro
---------------