100 SYS 700
110 ;PAUL G. SAWYER
120 ;
130 ;ORANGEVILLE, ON
140 ;
150 ;
160 ;DEVICE PRESENCE CHECKER
170 ;-----(RELOCATABLE)-----
180 ;PUT DEVICE # IN LOCATION 252
190 ;AFTER CALLING ROUTINE, READ
200 ;LOCATION 251. IF ITS VALUE IS
210 ;0 THEN THE DEVICE IS OFF, OR
220 ;1 THEN THE DEVICE IS ON.
230 ;
240 ;NOTE- IF USING DEVICE 8 OR 9
250 ;AND DRIVE IS ON, THE ERROR LIGHT
260 ;WILL BE FLASHING, BUT JUST
270 ;INITIALIZE THE DRIVE AND ALL
280 ;WILL BE OK.
290 ;
300 *=$C000
310 .OPT OO
320 DEVICE = $FC
330 ONFLAG = $FB
340 LDA #0: STA ONFLAG
350 LDA DEVICE: TAX: LDY #0
360 JSR $FFBA   ;SETLFS
370 LDA #1: LDX ONFLAG: LDY #0
380 JSR $FFBD   ;SETNAM
390 JSR $FFC0   ;OPEN
400 LDA $90: PHA
410 LDA DEVICE: JSR $FFC3 ;CLOSE
420 PLA: BMI OFF
430 ON LDA #1: STA ONFLAG
440 OFF RTS