From 7939e38ed9a0a4fcd425423c5e3881eee7bc2ec2 Mon Sep 17 00:00:00 2001
From: Bruno Gouveia <bgouveia@gmail.com>
Date: Fri, 16 Nov 2018 22:06:33 +0000
Subject: [PATCH] T80: fixed DAA instruction (different from Z80)

---
 t80/T80_ALU.vhd | 79 +++++++++++++++++++++++++++++++++----------------
 1 file changed, 54 insertions(+), 25 deletions(-)

diff --git a/t80/T80_ALU.vhd b/t80/T80_ALU.vhd
index 17b9f0f..cdc6d61 100644
--- a/t80/T80_ALU.vhd
+++ b/t80/T80_ALU.vhd
@@ -216,35 +216,64 @@ begin
 			end if;
 		when "1100" =>
 			-- DAA
-			F_Out(Flag_H) <= F_In(Flag_H);
-			F_Out(Flag_C) <= F_In(Flag_C);
-			DAA_Q(7 downto 0) := unsigned(BusA);
-			DAA_Q(8) := '0';
-			if F_In(Flag_N) = '0' then
-				-- After addition
-				-- Alow > 9 or H = 1
-				if DAA_Q(3 downto 0) > 9 or F_In(Flag_H) = '1' then
-					if (DAA_Q(3 downto 0) > 9) then
-						F_Out(Flag_H) <= '1';
-					else
-						F_Out(Flag_H) <= '0';
+			if Mode = 3 then
+				F_Out(Flag_H) <= '0';
+				F_Out(Flag_C) <= F_In(Flag_C);
+				DAA_Q(7 downto 0) := unsigned(BusA);
+				DAA_Q(8) := '0';
+				if F_In(Flag_N) = '0' then
+					-- After addition
+					-- Alow > 9 or H = 1
+					if DAA_Q(3 downto 0) > 9 or F_In(Flag_H) = '1' then
+							DAA_Q := DAA_Q + 6;
+					end if;
+					-- new Ahigh > 9 or C = 1
+					if DAA_Q(8 downto 4) > 9 or F_In(Flag_C) = '1' then
+						DAA_Q := DAA_Q + 96; -- 0x60
+					end if;
+				else
+					-- After subtraction
+					if F_In(Flag_H) = '1' then
+						DAA_Q := DAA_Q - 6;
+						if F_In(Flag_C) = '0' then
+							DAA_Q(8) := '0';
+						end if;
+					end if;
+					if F_In(Flag_C) = '1' then
+						DAA_Q := DAA_Q - 96; -- 0x60
 					end if;
-					DAA_Q := DAA_Q + 6;
-				end if;
-				-- new Ahigh > 9 or C = 1
-				if DAA_Q(8 downto 4) > 9 or F_In(Flag_C) = '1' then
-					DAA_Q := DAA_Q + 96; -- 0x60
 				end if;
 			else
-				-- After subtraction
-				if DAA_Q(3 downto 0) > 9 or F_In(Flag_H) = '1' then
-					if DAA_Q(3 downto 0) > 5 then
-						F_Out(Flag_H) <= '0';
+				F_Out(Flag_H) <= F_In(Flag_H);
+				F_Out(Flag_C) <= F_In(Flag_C);
+				DAA_Q(7 downto 0) := unsigned(BusA);
+				DAA_Q(8) := '0';
+				if F_In(Flag_N) = '0' then
+					-- After addition
+					-- Alow > 9 or H = 1
+					if DAA_Q(3 downto 0) > 9 or F_In(Flag_H) = '1' then
+						if (DAA_Q(3 downto 0) > 9) then
+							F_Out(Flag_H) <= '1';
+						else
+							F_Out(Flag_H) <= '0';
+						end if;
+						DAA_Q := DAA_Q + 6;
+					end if;
+					-- new Ahigh > 9 or C = 1
+					if DAA_Q(8 downto 4) > 9 or F_In(Flag_C) = '1' then
+						DAA_Q := DAA_Q + 96; -- 0x60
+					end if;
+				else
+					-- After subtraction
+					if DAA_Q(3 downto 0) > 9 or F_In(Flag_H) = '1' then
+						if DAA_Q(3 downto 0) > 5 then
+							F_Out(Flag_H) <= '0';
+						end if;
+						DAA_Q(7 downto 0) := DAA_Q(7 downto 0) - 6;
+					end if;
+					if unsigned(BusA) > 153 or F_In(Flag_C) = '1' then
+						DAA_Q := DAA_Q - 352; -- 0x160
 					end if;
-					DAA_Q(7 downto 0) := DAA_Q(7 downto 0) - 6;
-				end if;
-				if unsigned(BusA) > 153 or F_In(Flag_C) = '1' then
-					DAA_Q := DAA_Q - 352; -- 0x160
 				end if;
 			end if;
 			F_Out(Flag_X) <= DAA_Q(3);