Gob's Program - SWTPC 6800 Assembly

;Gob's Program for the SWTPC 6800
;
;OUTCH - outputs character stored in acc. A to terminal
;INCH - inputs character from terminal into acc. A
;CONTRL - returns control to the monitor (to end the program)

OUTCH       EQU $E1D1
INCH        EQU $E1AC
CONTRL  EQU $E0E3

            ORG $0

GREET       FCC "Gob's Program: Y/N?"
MESSAGE FCC "PENUS "
NL          FCB $0D,$0A
ASK     FCC "? "
RESPONSE    RMB 1

            ORG $0800

            LDS #$7FF
main:       JSR newline

            LDX #$0
loop:       LDAA    GREET,X
            JSR OUTCH
            INX
            CPX #19     ;length of GREET
            BNE loop

            JSR newline

            LDX #$0
loop1:  LDAA    ASK,X
            JSR OUTCH
            INX
            CPX #2          ;length of ASK
            BNE loop1

poll:       JSR INCH
            CMPA    #33     ;only accept printed characters (above SPACE in ASCII)
            BMI poll
            STAA    RESPONSE

poll1:  JSR INCH
            CMPA    #13     ;13 = $0D = return key
            BNE poll1
            LDAA    RESPONSE
            CMPA    #89     ;'Y' = 89
            BNE main

forever:    JSR newline
            CLRB
line:       LDX #$0
loop2:  LDAA    MESSAGE,X
            JSR OUTCH
            INX
            CPX #6          ;length of MESSAGE
            BNE loop2
            INCB
            CMPB    #13     ;80 characters per line / length of MESSAGE ~= 13
            BNE line
            BRA forever

newline:    LDX #0          ;simple subroutine to print a newline
            LDAA    NL,X        ;takes no input but does destroy contents in X and A
            JSR OUTCH
            INX
            LDAA    NL,X
            JSR OUTCH
            RTS