From cabdbca11ed1563900683b0e9036dff294f49b61 Mon Sep 17 00:00:00 2001
From: lxpollitt <630494+lxpollitt@users.noreply.github.com>
Date: Thu, 11 Jun 2026 07:29:13 +0100
Subject: [PATCH] Fix envelope shape decoding for hold shapes 11, 13 and 15

The envelope shape register (R13) write handler contained an extra
assignment for the continue-plus-hold shapes: it overwrote the attack
state with the alternate bit's raw value before the envelope cycle
started. The attack state determines both the envelope's ramp
direction and, via the end-of-cycle handling, the level a holding
envelope holds at, so these shapes played wrong ramps and held at
wrong levels. Shape 13 (attack then hold at maximum) instead started
at maximum and faded to silence; shape 11 (decay then hold at
maximum) played an erratic scrambled ramp and held 6 dB low; shape 15
(attack then hold at silence) held at a loud level instead. Shape 9
survived only by coincidence, as the wrong assignment happens to
write the correct value for that shape.

The per-sample envelope code already implements the data sheet's hold
behaviour correctly when a cycle completes: it holds the last count,
or flips to the initial count first when both the Hold and Alternate
bits are set. The fix is simply to remove the bad assignment from the
write handler.

These shapes are reachable from Oric BASIC: PLAY envelope modes 5 and
7 map to shapes 11 and 13 via the ROM's envelope pattern table.
---
 html/src/main/java/emu/joric/gwt/GwtAYPSG.java | 3 ---
 1 file changed, 3 deletions(-)

diff --git a/html/src/main/java/emu/joric/gwt/GwtAYPSG.java b/html/src/main/java/emu/joric/gwt/GwtAYPSG.java
index a7c98b5..1789f67 100644
--- a/html/src/main/java/emu/joric/gwt/GwtAYPSG.java
+++ b/html/src/main/java/emu/joric/gwt/GwtAYPSG.java
@@ -400,9 +400,6 @@ public void writeRegister(int address, int value) {
             } else {
                 hold = value & 0x01;
                 alternate = value & 0x02;
-                if (hold != 0) {
-                    attack = alternate;
-                }
             }
             count[ENVELOPE] = period[ENVELOPE];
             countEnv = 0x0f;