The Microcontroller Idea Book - Jan Axelson's Lakeview Research

Chapter 7
Listing 7-4. Reads the data stored a a 4-digit address entered by the user on
a keypad.
1 REM lookup table stores the numeric value of each key
10 XBY(1F00H)=1 : REM 1
11 XBY(1F01H)=2 : REM 2
12 XBY(1F02H)=3 : REM 3
13 XBY(1F03H)=0CH :REM C
14 XBY(1F04H)=4 : REM 4
15 XBY(1F05H)=5 : REM 5
16 XBY(1F06H)=6 : REM 6
17 XBY(1F07H)=0DH :REM D
18 XBY(1F08H)=7 : REM 7
19 XBY(1F09H)=8 : REM 8
20 XBY(1F0AH)=9 : REM 9
21 XBY(1F0BH)=0EH :REM E
22 XBY(1F0CH)=0AH :REM A
23 XBY(1F0DH)=0 : REM 0
24 XBY(1F0EH)=0BH :REM B
25 XBY(1F0FH)=0FH :REM F
30 A=0
40 COUNT=3
50 PRINT “Please enter a 4-digit hex address to read: ”
60 DO
70 ONEX1 100
80 WHILE 1=1
90 END
100 KEY=XBY(0E000H).AND.0FH: REM read the key
110 DAT=XBY(1F00H+KEY): REM find its value
120 A=A+(DAT*(16**COUNT)): REM add to the total
130 COUNT=COUNT-1: REM keep track of # of digits read
140 PH0. DAT,
150 IF COUNT=-1 THEN GOSUB 200: wait for 4 digits
160 RETI
200 PRINT : PH0. XBY(A)," is stored at address “,A
210 PRINT “Please enter another 4-digit address to read: ”
220 COUNT=3
230 A=0
240 RETI
124 The Microcontroller Idea Book