From 20adc731c24b8be2f7b963c8ed6a41829f7f5617 Mon Sep 17 00:00:00 2001
From: arbee <rb6502@users.noreply.github.com>
Date: Thu, 6 Jan 2022 20:27:01 -0500
Subject: [PATCH] es5503: fix interpretation of oscillator enable register.
 (GitHub bug #9045) [R. Belmont]

---
 src/devices/sound/es5503.cpp | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/src/devices/sound/es5503.cpp b/src/devices/sound/es5503.cpp
index 4efe61a0d7d..d4fc9a422ef 100644
--- a/src/devices/sound/es5503.cpp
+++ b/src/devices/sound/es5503.cpp
@@ -2,7 +2,7 @@
 // copyright-holders:R. Belmont
 /*
 
-  ES5503 - Ensoniq ES5503 "DOC" emulator v2.1.2
+  ES5503 - Ensoniq ES5503 "DOC" emulator v2.1.3
   By R. Belmont.
 
   Copyright R. Belmont.
@@ -33,6 +33,7 @@
   2.1.2 (RB) - Fixed SoundSmith POLY.SYNTH inst where one-shot on the even oscillator and swap on the odd should loop.
                Conversely, the intro voice in FTA Delta Demo has swap on the even and one-shot on the odd and doesn't
                want to loop.
+  2.1.3 (RB) - Fixed oscillator enable register off-by-1 which caused everything to be half a step sharp.
 */
 
 #include "emu.h"
@@ -144,7 +145,7 @@ void es5503_device::sound_stream_update(sound_stream &stream, std::vector<read_s
 
 	for (int chan = 0; chan < output_channels; chan++)
 	{
-		for (osc = 0; osc < (oscsenabled+1); osc++)
+		for (osc = 0; osc < oscsenabled; osc++)
 		{
 			ES5503Osc *pOsc = &oscillators[osc];
 
@@ -231,7 +232,7 @@ void es5503_device::device_start()
 	save_pointer(STRUCT_MEMBER(oscillators, irqpend), 32);
 
 	oscsenabled = 1;
-	output_rate = (clock() / 8) / (2 + oscsenabled);
+	output_rate = (clock() / 8) / (oscsenabled + 2);
 	m_stream = stream_alloc(0, output_channels, output_rate);
 
 	m_timer = timer_alloc(0, nullptr);
@@ -239,7 +240,7 @@ void es5503_device::device_start()
 
 void es5503_device::device_clock_changed()
 {
-	output_rate = (clock() / 8) / (2 + oscsenabled);
+	output_rate = (clock() / 8) / (oscsenabled + 2);
 	m_stream->set_sample_rate(output_rate);
 
 	m_mix_buffer.resize((output_rate/50)*8);
@@ -427,7 +428,9 @@ void es5503_device::write(offs_t offset, u8 data)
 				break;
 
 			case 0xe1:  // oscillator enable
-				oscsenabled = (data>>1) & 0x1f;
+				// The number here is the number of oscillators to enable -1 times 2.  You can never
+				// have zero oscilllators enabled.  So a value of 62 enables all 32 oscillators.
+				oscsenabled = ((data>>1) & 0x3f) + 1;
 				notify_clock_changed();
 				break;