From ef227c1d96510356a2f2c4e11b800939ad89aa71 Mon Sep 17 00:00:00 2001
From: Gyorgy Szombathelyi <gyurco@freemail.hu>
Date: Mon, 19 Apr 2021 20:47:00 +0200
Subject: [PATCH] IremM62: add Lode Runner 3 topbottom mask

...for vertical scroll garbage supression
---
 Arcade_MiST/IremM62 Hardware/rtl/Graphics.VHD            | 1 +
 .../IremM62 Hardware/rtl/iremm62_video_controller.vhd    | 9 ++++++++-
 Arcade_MiST/IremM62 Hardware/rtl/platform.vhd            | 1 +
 3 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/Arcade_MiST/IremM62 Hardware/rtl/Graphics.VHD b/Arcade_MiST/IremM62 Hardware/rtl/Graphics.VHD
index 5e70698a..8e3b91e3 100644
--- a/Arcade_MiST/IremM62 Hardware/rtl/Graphics.VHD	
+++ b/Arcade_MiST/IremM62 Hardware/rtl/Graphics.VHD	
@@ -83,6 +83,7 @@ begin
 
       -- video data signals (in)
       rgb_i           => rgb_data,
+      topbottom_mask  => graphics_i.bit16(3)(0),
 
       -- video control signals (out)
       video_ctl_o     => from_video_ctl,
diff --git a/Arcade_MiST/IremM62 Hardware/rtl/iremm62_video_controller.vhd b/Arcade_MiST/IremM62 Hardware/rtl/iremm62_video_controller.vhd
index 0279faa7..e83db2fa 100644
--- a/Arcade_MiST/IremM62 Hardware/rtl/iremm62_video_controller.vhd	
+++ b/Arcade_MiST/IremM62 Hardware/rtl/iremm62_video_controller.vhd	
@@ -17,6 +17,7 @@ entity iremm62_video_controller is
 
     -- video input data
     rgb_i         : in RGB_t;
+    topbottom_mask: in std_logic;
 
     -- control signals (out)
     video_ctl_o   : out from_VIDEO_CTL_t;
@@ -82,7 +83,10 @@ begin
       -- display blank
       if hcnt = "00"&x"FF" then
         hblank1 <= '0';
-        if vcnt = '1'&x"00" then
+        if vcnt = '1'&x"00" and topbottom_mask = '0' then
+          vblank <= '0';
+        end if;
+        if vcnt = '1'&x"08" then
           vblank <= '0';
         end if;
       end if;
@@ -95,6 +99,9 @@ begin
       end if;
       if hcnt = "00"&x"87" then
         hblank2 <= '1';
+        if vcnt = '1'&x"F7" and topbottom_mask = '1' then
+          vblank <= '1';
+        end if;
         if vcnt = '1'&x"FF" then
           vblank <= '1';
         end if;
diff --git a/Arcade_MiST/IremM62 Hardware/rtl/platform.vhd b/Arcade_MiST/IremM62 Hardware/rtl/platform.vhd
index e5aceaf8..16aff7c5 100644
--- a/Arcade_MiST/IremM62 Hardware/rtl/platform.vhd	
+++ b/Arcade_MiST/IremM62 Hardware/rtl/platform.vhd	
@@ -552,6 +552,7 @@ begin
     graphics_o.bit16(0) <= scrollram_d_o when hwsel = HW_HORIZON else m62_hscroll;
     graphics_o.bit16(1) <= m62_vscroll;
     graphics_o.bit16(2) <= m62_vscroll2;
+    graphics_o.bit16(3)(0) <= m62_topbottom_mask;
   end block BLK_SCROLL;