From: Bernard Blackham <dagobah@ucc.asn.au>
Date: Fri, 15 Aug 2003 16:41:04 +0000 (+0000)
Subject: Rewrite of delay function
X-Git-Tag: ROMW~58
X-Git-Url: https://git.ucc.asn.au/?p=uccvend-snackrom.git;a=commitdiff_plain;h=8436ed0d04bf12d2478bffbe3ea45531fa954686

Rewrite of delay function
Riddance of print amount function (not needed for basic setup)
---

diff --git a/ROM2/helpers.c b/ROM2/helpers.c
index a35073c..b66f5ee 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 (
+		"loop:\n"
+		"	dex\n"                  /* 3 */
+		"	beq out\n"              /* 3 */
+		"	ldd #327\n"             /* 3 */
+		"inner_loop:\n" /* 15 cycles each */
+		"	cpd #0x0000\n"          /* 5 */
+		"	beq inner_loop_end\n"   /* 3 */
+		"	subd #0x0001\n"         /* 4 */
+		"	bra inner_loop\n"       /* 3 */
+		"inner_loop_end:\n"
+		"	bra loop\n"             /* 3 */
+		"out:\n"
+		"	pulb\n"
+		"	pula\n"
+		"	pulx\n");
 }
 
 void my_strncpy(char* dst, char* src, u8 max_size) {
diff --git a/ROM2/vectors.s b/ROM2/vectors.s
index f420128..f8f586d 100644
--- a/ROM2/vectors.s
+++ b/ROM2/vectors.s
@@ -35,8 +35,8 @@ Boston, MA 02111-1307, USA.  */
 def:
 	rti
 
-	.globl _debug_user_vectors
-_debug_user_vectors = 0
+;;	.globl _debug_user_vectors
+;;_debug_user_vectors = 0
 
 
 ;; RTI interrupt handler
diff --git a/ROM2/vend.h b/ROM2/vend.h
index 9922719..f3b0e65 100644
--- a/ROM2/vend.h
+++ b/ROM2/vend.h
@@ -30,7 +30,6 @@ extern u16 _stack;
 
 /******* from helpers.c *******/
 void delay(u16 ms);
-void print_amount(u16 amt);
 void my_strncpy(char* dst, char* src, u8 max_size); /* for null-term strings */
 void my_memcpy(char* dst, char* src, u8 size);