add credit, add 013 debug timer message on keypress

[uccvend-snackrom.git] / ROM2 / start.s

diff --git a/ROM2/start.s b/ROM2/start.s
index 1520835..c3f8d36 100644 (file)
--- a/ROM2/start.s
+++ b/ROM2/start.s
@@ -2,24 +2,46 @@
 .globl _start
 
 _start:
-;; enable the RTI
+       ;; set port a to output
+       ldab #0xfc  ; 11111000
+       stab 0x1001
+
+       ;; start chiming
+       ldx #0x1000
+       bset 00,x #0x10
+
+       ;; enable the RTI
        ldaa #0x40
        staa 0x1024
-;; enable the ADC, and configure IRQ' for edge-sensitive operation
+
+       ;; enable the ADC, and configure IRQ' for edge-sensitive operation
        ldaa #0xa0
        staa 0x1039
-;; set the stack pointer
-       lds _stack
 
-;; initialize initialised variables
+       ;; set RTI intervals, and PA3/7 DDRs
+       ldaa #0x81
+       staa 0x1026  ;; RTI interval becomes E/2^14 = 6.6ms (or 150 Hz)
+
+       ;; clear ADC register
+       clra
+       staa 0x1030
+
+       ;; set the stack pointer
+       lds #_stack
+
+       ;; blank initialised variables - should match memory.x's page0
        ldx #0x0000
-loop:
-       cpx #0x0080
-       bcc out
+loop1:
+       cpx #0x0100
+       bcc out1
        clr 00,x
        inx
-       bra loop
-out:
+       bra loop1
+out1:
+
+       ;; stop chiming
+       ldx #0x1000
+       bclr 00,x #0x10
 
        jsr main