Apple2: implement sleep using MONWAIT

Also publish detect_iigs(), set_iigs_speed() and get_iigs_speed(). Refactor to only store one ostype variable.

libsrc/apple2/sleep.s

@@ -0,0 +1,54 @@
+;
+; Colin Leroy-Mira <colin@colino.net>, 2024
+;
+; void __fastcall__ sleep(unsigned s)
+;
+;
+
+        .export         _sleep
+        .import         _get_iigs_speed
+        .import         _set_iigs_speed
+        .import         WAIT
+        .importzp       tmp1
+
+        .include        "accelerator.inc"
+
+        ; This functions uses the Apple2 WAIT ROM routine to waste a certain
+        ; amount of cycles and returns approximately after the numbers of
+        ; seconds passed in AX.
+        ;
+        ; It takes 1023730 cycles when called with AX=1 (1,0007s),
+        ; 10236364 cycles when called with AX=10 (10,006 seconds),
+        ; 306064298 cycles with AX=300 (299.2 seconds).
+        ;
+        ; Caveat: IRQs firing during calls to sleep will make the sleep longer
+        ; by the amount of cycles it takes to handle the IRQ.
+        ;
+_sleep:
+        stx     tmp1            ; High byte of s in X
+        tay                     ; Low byte in A
+        ora     tmp1
+        bne     :+
+        rts
+:       jsr     _get_iigs_speed ; Save current CPU speed
+        pha
+        lda     #SPEED_SLOW     ; Down to 1MHz for consistency around WAIT
+        jsr     _set_iigs_speed
+sleep_1s:
+        ldx     #$0A            ; Loop 10 times
+sleep_100ms:
+        lda     #$C7            ; Sleep about 99ms
+        jsr     WAIT
+        lda     #$0D             ; About 1ms
+        jsr     WAIT
+        dex
+        bne     sleep_100ms
+        dey
+        bne     sleep_1s
+        dec     tmp1
+        bmi     done
+        dey                     ; Down to #$FF
+        bne     sleep_1s
+done:
+        pla                     ; Restore CPU speed
+        jmp     _set_iigs_speed