From 32563970c25265aee4325db14d9f1f12bc0ce628 Mon Sep 17 00:00:00 2001
From: SarahW <pcem@pcem-emulator.co.uk>
Date: Tue, 18 Feb 2020 12:08:53 +0000
Subject: [PATCH] Bit 0 of port 3da on Amstrad PC1512 is a toggle bit instead
 of display enable.

---
 src/vid_pc1512.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/src/vid_pc1512.c b/src/vid_pc1512.c
index afe3c5d..3c962d0 100644
--- a/src/vid_pc1512.c
+++ b/src/vid_pc1512.c
@@ -107,7 +107,8 @@ static uint8_t pc1512_in(uint16_t addr, void *p)
                 case 0x3d5:
                 return pc1512->crtc[pc1512->crtcreg];
                 case 0x3da:
-                return pc1512->stat;
+                pc1512->stat ^= 0x01; /*Bit 0 is toggle bit on PC1512*/
+                return pc1512->stat ^ 0x01;
         }
         return 0xff;
 }
@@ -174,7 +175,6 @@ static void pc1512_poll(void *p)
         if (!pc1512->linepos)
         {
                 timer_advance_u64(&pc1512->timer, pc1512->dispofftime);
-                pc1512->stat |= 1;
                 pc1512->linepos = 1;
                 oldsc = pc1512->sc;
                 if (pc1512->dispon)
@@ -342,8 +342,6 @@ static void pc1512_poll(void *p)
                 timer_advance_u64(&pc1512->timer, pc1512->dispontime);
                 if ((pc1512->lastline - pc1512->firstline) == 199) 
                         pc1512->dispon = 0; /*Amstrad PC1512 always displays 200 lines, regardless of CRTC settings*/
-                if (pc1512->dispon) 
-                        pc1512->stat &= ~1;
                 pc1512->linepos = 0;
                 if (pc1512->vsynctime)
                 {