Nuts and Volts - July/August 2018

Vintage Computing

70 n=FILE
75 DISPLAY n
80 IF n>-1 THEN GOTO 70
85 DISPLAY 13,13: PRINT “Closing file...”
90 CLOSE

of the Propeller system counter register. For the 80 MHz system clock of the Amigo, each tick of the clock is close to 0.125 nanoseconds, so you can use CNT to perform some timing tasks in your programs.

WORD and LONG work just like the BYTE command, but with a two-byte or four-byte operand, respectively. Try these commands on the video section of the main memory. As expected, WORD ignores the top two bytes of the 32-bit variable S, while LONG uses all four. You may find these two commands helpful for some tasks with your Amigo.

It won’t be gnat’s eyebrow precise due to the double-interpreted nature of Color BASIC, but may be close enough for some of your programming needs. This next code block (also in the downloads) creates a crude stopwatch by counting clock ticks and doing some math:

CLS
S = “A””SHL 24 + “B””SHL 16 + “C””SHL 8 + “D”
WORD [2850] = S CD
LONG [2800] = S ABCD
PRINT WORD [2850]
16706
PRINT WORD [2800]
538976288
 10 REM —- TIMER.BAS —-
 15 CLS : PRINT “Press any key to start...”
 20 IF INKEY =0 THEN GOTO 20
 25 a = CNT
 30 CLS : PRINT “Press any key to stop...”
 35 LOCATE 15,15: PRINT “CNT = “;CNT
 40 IF INKEY =0 THEN GOTO 35
 45 b=CNT
 50 CLS
 55 PRINT “Start CNT  = “;a
 60 PRINT “Stop CNT = “;b
 65 PRINT “Difference = “;b-a
 70 t=(b-a)/100000*125
 75 s=t/100000