From 2ab4b351cae620953e948d9d10c8af59f5368705 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Tue, 27 Dec 2022 22:20:47 -0500
Subject: [PATCH] Extend enum.

---
 Components/9918/9918.cpp                    | 15 ++++++++++++++-
 Components/9918/Implementation/9918Base.hpp |  3 +++
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/Components/9918/9918.cpp b/Components/9918/9918.cpp
index 85e6c7eca..7527b9c64 100644
--- a/Components/9918/9918.cpp
+++ b/Components/9918/9918.cpp
@@ -33,7 +33,20 @@ using namespace TI::TMS;
 //		1368 = 2 * 2 * 2	*	3 * 3	* 			19
 //
 //	=> 2^3 * 3^2 * 5 * 19 = 6840
-//		... which
+//		... which would imply a multiply by 30 on the input clock if
+//		it were to remain 3.58Mhz.
+
+// Mega Drive notes, assorted:
+//
+//
+//
+// there are 60 EDCLK at MCLK/5 during a line ... like this:
+//
+//	15 @ /5; 2 @ /4; 15 @ /5; 2 @ /4; 15 @ /5; 2 @ /4; 15 @ /5
+//
+// ... HSYNC signal is what triggers the changes in EDCLK frequency, with some latency though.
+//
+// The total is still 840 EDCLKS (420 pixels) with 780 @MCLK/4 and 60@MCLK/5 (total is 3420 MCLCKS).
 
 namespace {
 
diff --git a/Components/9918/Implementation/9918Base.hpp b/Components/9918/Implementation/9918Base.hpp
index c0bb8c86d..fb09f3215 100644
--- a/Components/9918/Implementation/9918Base.hpp
+++ b/Components/9918/Implementation/9918Base.hpp
@@ -24,9 +24,12 @@ enum Personality {
 	TMS9918A,	// includes the 9928 and 9929; set TV standard and output device as desired.
 	V9938,
 	V9958,
+
+	// Sega extensions.
 	SMSVDP,
 	SMS2VDP,
 	GGVDP,
+	MDVDP,
 };
 
 enum class TVStandard {