[EXTMEM-3
[KEYBOARD ENTRY CONTROLS FUNCTIONS
[ A = SET NEW ADDRESS IN EXTERNAL MEMORY FROM CONTENTS OF RIGHT SWITCHES, 0000 TO 3777
[ W = WRITE CONTENTS OF QUARTERS 4 AND 5 INTO EXTERNAL MEMORY, STARTING AT THE PREVIOUSLY SPECIFIED ADDRESS
[ R = READ FROM EXTERNAL MEMORY INTO QUATERS 6 AND 7
$20
[DISPLAY BEGINS
#1B SETi1
3777
SETi2
2777
SETi3
4777
#1C LDAi1
DIS 1
LDAi2
DISi3
XSK 3
JMP 1C
KST
JMP 1B
[IF KEY HAS BEEN STRUCK
KBDi
SHDi
5200
JMP 1W
SHDi
4500
JMP 1R
SHDi
2400
JMP 1A
JMP 1B
[WRITE
#1W LDAi
3000
OPR 0
SETi1
3777
LDAi1
OPR 4
XSK 1
JMP p-3
JMP 1B
[READ
#1R LDAi
3000
OPR 0
SETi2
2777
OPR 3
STAi2
XSK 2
JMP p-3
JMP 1B
[ADDRESS
#1A RSW
STA
1R+1
STC 1W+1
JMP 1B
[END FOR NOW