X-Git-Url: https://git.ucc.asn.au/?a=blobdiff_plain;f=ROM2%2Fhelpers.c;h=5f0da09c9770b2706e9f61bec11213d25cd47900;hb=b14807a016c121bc79efd5702ffba33c1dbd9be2;hp=a35073cf5ca7400a177f08ff1e9127238fcfe7b5;hpb=2e7a8beb908896930042bc0564fbd16f3e0b0b62;p=uccvend-snackrom.git

diff --git a/ROM2/helpers.c b/ROM2/helpers.c
index a35073c..5f0da09 100644
--- a/ROM2/helpers.c
+++ b/ROM2/helpers.c
@@ -1,23 +1,32 @@
 #include "display_basic.h"
 #include "vend.h"
 
-#define DELAY_MAGIC 20 /* FIXME: number of loops for ~ 1 millisecond (< 256) */
 void delay(u16 ms) {
-	u8 i;
-	for (;ms;ms--) {
-		for (i=0;i<DELAY_MAGIC; i++)
-			asm("nop\nnop\nnop\nnop\nnop\n");
-	}
-}
-
-void print_amount(u16 amt) {
-	/* take amt and show it on screen with a $ sign */
-	char str[10] = {' ', '$', ' ', ' ', ' ', ' ', ' ', ' ', ' ', ' '};
-	u8 pos;
-	for (pos = 7; amt; pos--, amt/=10) {
-		str[pos] = amt%10 + '0';
-	}
-	set_msg(str);
+	/* delay routine written in assembly so we know what we're really getting.
+	 * each inner loop should take ~1 ms to execute.
+	 * 15 cycles * (1/4.9152Mhz) * 327 = 0.997 ms + a little bit on the fringes.
+	 *
+	 * XXX - how do we know gcc isn't optimising this? it seems to optimise after
+	 * parsing C -> asm, but before asm -> machine code.
+	 */
+	//asm volatile ("pshx\npsha\npshb\n"); /* save registers */
+	asm volatile ("ldx %0\n" :: "m" (ms));
+	asm volatile (
+		"delay_loop:\n"
+		"	dex\n"                        /* 3 */
+		"	beq delay_out\n"              /* 3 */
+		"	ldd #327\n"                   /* 3 */
+		"delay_inner_loop:\n" /* 15 cycles each */
+		"	cpd #0x0000\n"                /* 5 */
+		"	beq delay_inner_loop_end\n"   /* 3 */
+		"	subd #0x0001\n"               /* 4 */
+		"	bra delay_inner_loop\n"       /* 3 */
+		"delay_inner_loop_end:\n"
+		"	bra delay_loop\n"             /* 3 */
+		"delay_out:\n");
+		/*"	pulb\n"
+		"	pula\n"
+		"	pulx\n");*/
 }
 
 void my_strncpy(char* dst, char* src, u8 max_size) {