X-Git-Url: http://gitweb.hugovil.com/?a=blobdiff_plain;f=src%2Fcpu8051.c;h=1fd02514f5c0455431554dcae406e5696dec67b6;hb=ce24c216aa7eaf099dda2c9efeb9603a4076c93e;hp=30c8cca7c1a9863afe8c28f6984a8462c9d47106;hpb=dd92f3969f3537fc1dd13926e7ae1014d27513ab;p=emu8051.git

diff --git a/src/cpu8051.c b/src/cpu8051.c
index 30c8cca..1fd0251 100644
--- a/src/cpu8051.c
+++ b/src/cpu8051.c
@@ -283,18 +283,27 @@ process_timer(uint8_t tl, uint8_t th, uint8_t tf_mask, uint8_t TR, uint8_t mode,
 	      uint8_t GATE, uint32_t TimerCounter)
 {
 	unsigned int tmp;
+	unsigned int prescaler;
 
 	switch (mode) {
 	case 0:
-		/* Mode 0, 13-bits counter. */
-		tmp = cpu8051_ReadD(th) * 0x100 + cpu8051_ReadD(tl);
-		tmp++;
-		tmp &= 0x1FFF; /* We keep only 13 bits */
-
-		if (tmp == 0)  /* If overflow set TF0 */
-			cpu8051_WriteD(_TCON_, cpu8051_ReadD(_TCON_) | tf_mask);
-		cpu8051_WriteD(_TH0_, tmp / 0x100);
-		cpu8051_WriteD(_TL0_, tmp & 0xFF);
+		/* Mode 0, 8-bit timer "TH" with "TL" as 5-bit prescaler. */
+		prescaler = cpu8051_ReadD(tl);
+		prescaler++;
+		prescaler &= 0x1F; /* We keep only 5 bits */
+		cpu8051_WriteD(tl, prescaler);
+
+		if (prescaler == 0) {
+			/* If overflow, increment TH */
+			tmp = cpu8051_ReadD(th);
+			tmp++;
+			tmp &= 0xFF; /* We keep only 8 bits */
+
+			if (tmp == 0)  /* If overflow set TF */
+				cpu8051_WriteD(_TCON_, cpu8051_ReadD(_TCON_) | tf_mask);
+
+			cpu8051_WriteD(th, tmp);
+		}
 		break;
 	case 1:
 		/* Mode 1, 16-bits counter */
@@ -303,8 +312,8 @@ process_timer(uint8_t tl, uint8_t th, uint8_t tf_mask, uint8_t TR, uint8_t mode,
 		tmp &= 0xFFFF; /* We keep only 16 bits */
 		if (tmp == 0) /* If overflow set TF0 */
 			cpu8051_WriteD(_TCON_, cpu8051_ReadD(_TCON_) | tf_mask);
-		cpu8051_WriteD(_TH0_, (tmp / 0x100));
-		cpu8051_WriteD(_TL0_, (tmp & 0xFF));
+		cpu8051_WriteD(th, (tmp / 0x100));
+		cpu8051_WriteD(tl, (tmp & 0xFF));
 		break;
 	case 2:
 		/* Mode 2, 8-bits counter with Auto-Reload */
@@ -492,7 +501,7 @@ cpu8051_get_instruction_size(unsigned char opcode)
 	return InstSizesTbl[opcode];
 }
 
-/* Display instruction menmonic. */
+/* Display instruction mnemonic. */
 void
 cpu8051_disasm_mnemonic(unsigned char OpCode, char *buf)
 {
@@ -630,7 +639,7 @@ cpu8051_Disasm(unsigned int Address, char *Text)
 	for (; len < 17;)
 		len += sprintf(&Text[len], " ");
 
-	/* Display instruction menmonic. */
+	/* Display instruction mnemonic. */
 	len += sprintf(&Text[len], "%s ",
 			      InstTextTbl[InstTypesTbl[OpCode]]);
 	ArgTblOfs = OpCode << 2;