X-Git-Url: https://git.ucc.asn.au/?a=blobdiff_plain;f=ROM2%2Fstart.s;h=c3f8d36f843ee6ed447d81233b4a60d5f5036ffc;hb=HEAD;hp=1520835f5808519932eab53f3a887a207b2bb535;hpb=3d8e5e4e1024a34885544acf3acec80e1b1e732b;p=uccvend-snackrom.git

diff --git a/ROM2/start.s b/ROM2/start.s
index 1520835..c3f8d36 100644
--- 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