From a9665dd8a88577079ca28a82abfbcdca62c0ce87 Mon Sep 17 00:00:00 2001
From: Zane Kaminski <zanekaminski@gmail.com>
Date: Wed, 9 Oct 2024 08:00:35 -0400
Subject: [PATCH] Add back 68k clock gated slowdown

---
 cpld/CNT.v    | 12 +++++++++++-
 cpld/WarpSE.v |  8 ++++----
 2 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/cpld/CNT.v b/cpld/CNT.v
index 2952643..ef32620 100644
--- a/cpld/CNT.v
+++ b/cpld/CNT.v
@@ -8,12 +8,15 @@ module CNT(
 	/* Mac PDS bus master control outputs */
 	output reg AoutOE, output reg nBR_IOB,
 	/* QoS select inputs */
+	input nAS,
+	input ASrf,
 	input BACT,
 	input QoSCS,
 	input SndQoSCS,
 	/* QoS outputs */
 	output reg QoSEN,
-	output SndQoSReady);
+	output SndQoSReady,
+	output reg MCKE);
 	
 	/* E clock synchronization */
 	reg [1:0] Er; always @(posedge CLK) Er[1:0] <= { Er[0], E };
@@ -21,6 +24,7 @@ module CNT(
 	
 	/* C8M clock synchronization */
 	reg [3:0] C8Mr; always @(posedge CLK) C8Mr[3:0] <= { C8Mr[2:0], C8M };
+	wire C8MFall =  C8Mr[1] && !C8Mr[0]; // C8M falling edge detect
 	
 	/* Timer counts from 0 to 1010 (10) -- 11 states == 14.042 us
     *	Refresh timer sequence
@@ -73,6 +77,12 @@ module CNT(
 	always @(posedge CLK) if (!BACT) QoSEN <= QS!=0;
 	assign SndQoSReady = 1;
 	
+	/* MC68k clock gating during QoS */
+	always @(negedge CLK, negedge nAS) begin
+		if (!nAS) MCKE <= 1;
+		else MCKE <= ASrf || !QoSEN || C8MFall;
+	end
+	
 	/* Long timer counts from 0 to 4095.
 	 * 4096 states == 57.516 ms */
 	reg [11:0] LTimer;
diff --git a/cpld/WarpSE.v b/cpld/WarpSE.v
index 498023f..fa274d1 100644
--- a/cpld/WarpSE.v
+++ b/cpld/WarpSE.v
@@ -41,9 +41,6 @@ module WarpSE(
 	output MCKE,
 	input [5:0] DBG);
 
-	/* MC68k clock enable */
-	assign MCKE = 1;
-
 	/* GA gated (translated) address output */
 	assign GA[23:22] = A_FSB[23:22];
 	/*assign GA[23:22] = (
@@ -218,12 +215,15 @@ module WarpSE(
 		.AoutOE(AoutOE),
 		.nBR_IOB(nBR_IOBout),
 		/* QoS select inputs */
+		.nAS(nAS_FSB),
+		.ASrf(ASrf),
 		.BACT(BACT),
 		.QoSCS(QoSCS),
 		.SndQoSCS(SndQoSCS),
 		/* QoS outputs */
 		.QoSEN(QoSEN),
-		.SndQoSReady(SndQoSReady));
+		.SndQoSReady(SndQoSReady),
+		.MCKE(MCKE));
 	
 	FSB fsb(
 		/* MC68HC000 interface */