From 1f4d526ea5227382a7463897406be31f52e21050 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Sat, 29 Apr 2023 23:48:22 -0400
Subject: [PATCH] Permit MSX RAM mapper readback.

---
 Machines/MSX/MSX.cpp | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/Machines/MSX/MSX.cpp b/Machines/MSX/MSX.cpp
index afa84e143..b36150929 100644
--- a/Machines/MSX/MSX.cpp
+++ b/Machines/MSX/MSX.cpp
@@ -595,6 +595,13 @@ class ConcreteMachine:
 								*cycle.value = clock_.read(next_clock_register_);
 							break;
 
+							case 0xfc: case 0xfd: case 0xfe: case 0xff:
+								if constexpr (model != Target::Model::MSX1) {
+									*cycle.value = ram_mapper_[(address & 0xff) - 0xfc];
+									break;
+								}
+								[[fallthrough]];
+
 							default:
 //								printf("Unhandled read %02x\n", address & 0xff);
 								*cycle.value = 0xff;
@@ -643,6 +650,8 @@ class ConcreteMachine:
 									break;
 								}
 
+								ram_mapper_[port - 0xfc] = *cycle.value;
+
 								// Apply to RAM.
 								//
 								// On a real MSX this may also affect other slots.
@@ -877,6 +886,7 @@ class ConcreteMachine:
 		// 8kb resolution is used by some cartride titles.
 		const uint8_t *read_pointers_[8];
 		uint8_t *write_pointers_[8];
+		uint8_t ram_mapper_[4]{};
 
 		/// Optionally attaches non-default logic to any of the four things selectable
 		/// via the primary slot register.