From df143446696cee294a6ffd7ea6bc0b09a43d9c02 Mon Sep 17 00:00:00 2001
From: AJR <ajrhacker@users.noreply.github.com>
Date: Fri, 15 Nov 2019 15:35:10 -0500
Subject: [PATCH] 65C02 opcode timing and bus usage corrections - BBR and BBS
 use one or two extra cycles when the branch is taken, like other conditional
 branches - TRB and TSB perform an extra read of the operand instead of an
 extra write

---
 src/devices/cpu/m6502/om65c02.lst | 16 ++++++++++++----
 1 file changed, 12 insertions(+), 4 deletions(-)

diff --git a/src/devices/cpu/m6502/om65c02.lst b/src/devices/cpu/m6502/om65c02.lst
index d5428557344..3e414cd7bfd 100644
--- a/src/devices/cpu/m6502/om65c02.lst
+++ b/src/devices/cpu/m6502/om65c02.lst
@@ -163,6 +163,10 @@ bbr_zpb
 	read(TMP);
 	TMP = read_pc();
 	if(!(TMP2 & (1 << ((inst_state >> 4) & 7)))) {
+		read_pc_noinc();
+		if(page_changing(PC, int8_t(TMP))) {
+			read_arg(set_l(PC, PC+int8_t(TMP)));
+		}
 		PC += int8_t(TMP);
 	}
 	prefetch();
@@ -173,6 +177,10 @@ bbs_zpb
 	read(TMP);
 	TMP = read_pc();
 	if(TMP2 & (1 << ((inst_state >> 4) & 7))) {
+		read_pc_noinc();
+		if(page_changing(PC, int8_t(TMP))) {
+			read_arg(set_l(PC, PC+int8_t(TMP)));
+		}
 		PC += int8_t(TMP);
 	}
 	prefetch();
@@ -709,7 +717,7 @@ trb_aba
 	TMP = read_pc();
 	TMP = set_h(TMP, read_pc());
 	TMP2 = read(TMP);
-	write(TMP, TMP2);
+	read(TMP);
 	if(A & TMP2)
 		P &= ~F_Z;
 	else
@@ -721,7 +729,7 @@ trb_aba
 trb_zpg
 	TMP = read_pc();
 	TMP2 = read(TMP);
-	write(TMP, TMP2);
+	read(TMP);
 	if(A & TMP2)
 		P &= ~F_Z;
 	else
@@ -734,7 +742,7 @@ tsb_aba
 	TMP = read_pc();
 	TMP = set_h(TMP, read_pc());
 	TMP2 = read(TMP);
-	write(TMP, TMP2);
+	read(TMP);
 	if(A & TMP2)
 		P &= ~F_Z;
 	else
@@ -746,7 +754,7 @@ tsb_aba
 tsb_zpg
 	TMP = read_pc();
 	TMP2 = read(TMP);
-	write(TMP, TMP2);
+	read(TMP);
 	if(A & TMP2)
 		P &= ~F_Z;
 	else