From 39232f00f1130d54a9d260c1d1c872a807068317 Mon Sep 17 00:00:00 2001
From: Dean Netherton <dinoboards@netherton.org>
Date: Wed, 24 Jul 2024 16:23:18 +1000
Subject: [PATCH] sn76489: added configuration entry SN76489CHNOUT to direct to
 only to one channel or both

---
 Source/HBIOS/cfg_duo.asm      |  1 +
 Source/HBIOS/cfg_dyno.asm     |  1 +
 Source/HBIOS/cfg_epitx.asm    |  1 +
 Source/HBIOS/cfg_heath.asm    |  1 +
 Source/HBIOS/cfg_master.asm   |  1 +
 Source/HBIOS/cfg_mbc.asm      |  1 +
 Source/HBIOS/cfg_mk4.asm      |  1 +
 Source/HBIOS/cfg_mon.asm      |  1 +
 Source/HBIOS/cfg_n8.asm       |  1 +
 Source/HBIOS/cfg_nabu.asm     |  1 +
 Source/HBIOS/cfg_rcez80.asm   |  1 +
 Source/HBIOS/cfg_rcz180.asm   |  1 +
 Source/HBIOS/cfg_rcz280.asm   |  1 +
 Source/HBIOS/cfg_rcz80.asm    |  1 +
 Source/HBIOS/cfg_rph.asm      |  1 +
 Source/HBIOS/cfg_s100.asm     |  1 +
 Source/HBIOS/cfg_sbc.asm      |  1 +
 Source/HBIOS/cfg_scz180.asm   |  1 +
 Source/HBIOS/cfg_z80retro.asm |  1 +
 Source/HBIOS/cfg_zeta.asm     |  1 +
 Source/HBIOS/cfg_zeta2.asm    |  1 +
 Source/HBIOS/sn76489.asm      | 20 +++++++++++++-------
 Source/HBIOS/std.asm          |  6 ++++++
 23 files changed, 40 insertions(+), 7 deletions(-)

diff --git a/Source/HBIOS/cfg_duo.asm b/Source/HBIOS/cfg_duo.asm
index 979f32ae..3bc052ea 100644
--- a/Source/HBIOS/cfg_duo.asm
+++ b/Source/HBIOS/cfg_duo.asm
@@ -306,6 +306,7 @@ UFENABLE	.EQU	FALSE		; UF: ENABLE ECB USB FIFO DRIVER (UF.ASM)
 UFBASE		.EQU	$0C		; UF: REGISTERS BASE ADR
 ;
 SN76489ENABLE	.EQU	FALSE		; SN: ENABLE SN76489 SOUND DRIVER
+SN76489CHNOUT	.EQU	SNCHAN_BOTH	; SN: CHANNEL OUTPUTS: SNCHAN_[BOTH|LEFT|RIGHT]
 AUDIOTRACE	.EQU	FALSE		; ENABLE TRACING TO CONSOLE OF SOUND DRIVER
 SN7CLK		.EQU	3579545		; SN: PSG CLOCK FREQ, ASSUME MSX STD
 SNMODE		.EQU	SNMODE_DUO	; SN: DRIVER MODE: SNMODE_[NONE|RC|VGM|DUO]
diff --git a/Source/HBIOS/cfg_dyno.asm b/Source/HBIOS/cfg_dyno.asm
index b37b2222..3cc02f97 100644
--- a/Source/HBIOS/cfg_dyno.asm
+++ b/Source/HBIOS/cfg_dyno.asm
@@ -285,6 +285,7 @@ PIO_SBC		.EQU	FALSE		; PIO: ENABLE PARALLEL PORT DRIVER FOR 8255 CHIP
 UFENABLE	.EQU	FALSE		; UF: ENABLE ECB USB FIFO DRIVER (UF.ASM)
 ;
 SN76489ENABLE	.EQU	FALSE		; SN: ENABLE SN76489 SOUND DRIVER
+SN76489CHNOUT	.EQU	SNCHAN_BOTH	; SN: CHANNEL OUTPUTS: SNCHAN_[BOTH|LEFT|RIGHT]
 AUDIOTRACE	.EQU	FALSE		; ENABLE TRACING TO CONSOLE OF SOUND DRIVER
 SN7CLK		.EQU	3579545		; SN: PSG CLOCK FREQ, ASSUME MSX STD
 SNMODE		.EQU	SNMODE_NONE	; SN: DRIVER MODE: SNMODE_[NONE|RC|VGM]
diff --git a/Source/HBIOS/cfg_epitx.asm b/Source/HBIOS/cfg_epitx.asm
index 8bdd7d04..240eb5b2 100644
--- a/Source/HBIOS/cfg_epitx.asm
+++ b/Source/HBIOS/cfg_epitx.asm
@@ -317,6 +317,7 @@ PIO_SBC		.EQU	FALSE		; PIO: ENABLE PARALLEL PORT DRIVER FOR 8255 CHIP
 UFENABLE	.EQU	FALSE		; UF: ENABLE ECB USB FIFO DRIVER (UF.ASM)
 ;
 SN76489ENABLE	.EQU	FALSE		; SN: ENABLE SN76489 SOUND DRIVER
+SN76489CHNOUT	.EQU	SNCHAN_BOTH	; SN: CHANNEL OUTPUTS: SNCHAN_[BOTH|LEFT|RIGHT]
 AUDIOTRACE	.EQU	FALSE		; ENABLE TRACING TO CONSOLE OF SOUND DRIVER
 SN7CLK		.EQU	3579545		; SN: PSG CLOCK FREQ, ASSUME MSX STD
 SNMODE		.EQU	SNMODE_RC	; SN: DRIVER MODE: SNMODE_[NONE|RC|VGM]
diff --git a/Source/HBIOS/cfg_heath.asm b/Source/HBIOS/cfg_heath.asm
index 2ef14948..b85556ba 100644
--- a/Source/HBIOS/cfg_heath.asm
+++ b/Source/HBIOS/cfg_heath.asm
@@ -310,6 +310,7 @@ PIO_SBC		.EQU	FALSE		; PIO: ENABLE PARALLEL PORT DRIVER FOR 8255 CHIP
 UFENABLE	.EQU	FALSE		; UF: ENABLE ECB USB FIFO DRIVER (UF.ASM)
 ;
 SN76489ENABLE	.EQU	FALSE		; SN: ENABLE SN76489 SOUND DRIVER
+SN76489CHNOUT	.EQU	SNCHAN_BOTH	; SN: CHANNEL OUTPUTS: SNCHAN_[BOTH|LEFT|RIGHT]
 AUDIOTRACE	.EQU	FALSE		; ENABLE TRACING TO CONSOLE OF SOUND DRIVER
 SN7CLK		.EQU	3579545		; SN: PSG CLOCK FREQ, ASSUME MSX STD
 SNMODE		.EQU	SNMODE_RC	; SN: DRIVER MODE: SNMODE_[NONE|RC|VGM]
diff --git a/Source/HBIOS/cfg_master.asm b/Source/HBIOS/cfg_master.asm
index 52be3841..1ef9fe79 100644
--- a/Source/HBIOS/cfg_master.asm
+++ b/Source/HBIOS/cfg_master.asm
@@ -377,6 +377,7 @@ UFENABLE	.EQU	FALSE		; UF: ENABLE ECB USB FIFO DRIVER (UF.ASM)
 UFBASE		.EQU	$0C		; UF: REGISTERS BASE ADR
 ;
 SN76489ENABLE	.EQU	FALSE		; SN: ENABLE SN76489 SOUND DRIVER
+SN76489CHNOUT	.EQU	SNCHAN_BOTH	; SN: CHANNEL OUTPUTS: SNCHAN_[BOTH|LEFT|RIGHT]
 AUDIOTRACE	.EQU	FALSE		; ENABLE TRACING TO CONSOLE OF SOUND DRIVER
 SN7CLK		.EQU	3579545		; SN: PSG CLOCK FREQ, ASSUME MSX STD
 SNMODE		.EQU	SNMODE_NONE	; SN: DRIVER MODE: SNMODE_[NONE|RC|VGM]
diff --git a/Source/HBIOS/cfg_mbc.asm b/Source/HBIOS/cfg_mbc.asm
index 0f12e79e..80363530 100644
--- a/Source/HBIOS/cfg_mbc.asm
+++ b/Source/HBIOS/cfg_mbc.asm
@@ -293,6 +293,7 @@ UFENABLE	.EQU	FALSE		; UF: ENABLE ECB USB FIFO DRIVER (UF.ASM)
 UFBASE		.EQU	$0C		; UF: REGISTERS BASE ADR
 ;
 SN76489ENABLE	.EQU	FALSE		; SN: ENABLE SN76489 SOUND DRIVER
+SN76489CHNOUT	.EQU	SNCHAN_BOTH	; SN: CHANNEL OUTPUTS: SNCHAN_[BOTH|LEFT|RIGHT]
 AUDIOTRACE	.EQU	FALSE		; ENABLE TRACING TO CONSOLE OF SOUND DRIVER
 SN7CLK		.EQU	3579545		; SN: PSG CLOCK FREQ, ASSUME MSX STD
 SNMODE		.EQU	SNMODE_NONE	; SN: DRIVER MODE: SNMODE_[NONE|RC|VGM]
diff --git a/Source/HBIOS/cfg_mk4.asm b/Source/HBIOS/cfg_mk4.asm
index b8464158..9eb056eb 100644
--- a/Source/HBIOS/cfg_mk4.asm
+++ b/Source/HBIOS/cfg_mk4.asm
@@ -289,6 +289,7 @@ UFENABLE	.EQU	FALSE		; UF: ENABLE ECB USB FIFO DRIVER (UF.ASM)
 UFBASE		.EQU	$0C		; UF: REGISTERS BASE ADR
 ;
 SN76489ENABLE	.EQU	FALSE		; SN: ENABLE SN76489 SOUND DRIVER
+SN76489CHNOUT	.EQU	SNCHAN_BOTH	; SN: CHANNEL OUTPUTS: SNCHAN_[BOTH|LEFT|RIGHT]
 AUDIOTRACE	.EQU	FALSE		; ENABLE TRACING TO CONSOLE OF SOUND DRIVER
 SN7CLK		.EQU	3579545		; SN: PSG CLOCK FREQ, ASSUME MSX STD
 SNMODE		.EQU	SNMODE_VGM	; SN: DRIVER MODE: SNMODE_[NONE|RC|VGM]
diff --git a/Source/HBIOS/cfg_mon.asm b/Source/HBIOS/cfg_mon.asm
index cfc28dcc..d8c45232 100644
--- a/Source/HBIOS/cfg_mon.asm
+++ b/Source/HBIOS/cfg_mon.asm
@@ -315,6 +315,7 @@ PIO_SBC		.EQU	FALSE		; PIO: ENABLE PARALLEL PORT DRIVER FOR 8255 CHIP
 UFENABLE	.EQU	FALSE		; UF: ENABLE ECB USB FIFO DRIVER (UF.ASM)
 ;
 SN76489ENABLE	.EQU	FALSE		; SN: ENABLE SN76489 SOUND DRIVER
+SN76489CHNOUT	.EQU	SNCHAN_BOTH	; SN: CHANNEL OUTPUTS: SNCHAN_[BOTH|LEFT|RIGHT]
 AUDIOTRACE	.EQU	FALSE		; ENABLE TRACING TO CONSOLE OF SOUND DRIVER
 SN7CLK		.EQU	3579545		; SN: PSG CLOCK FREQ, ASSUME MSX STD
 SNMODE		.EQU	SNMODE_RC	; SN: DRIVER MODE: SNMODE_[NONE|RC|VGM]
diff --git a/Source/HBIOS/cfg_n8.asm b/Source/HBIOS/cfg_n8.asm
index a4979601..655894bc 100644
--- a/Source/HBIOS/cfg_n8.asm
+++ b/Source/HBIOS/cfg_n8.asm
@@ -282,6 +282,7 @@ UFENABLE	.EQU	FALSE		; UF: ENABLE ECB USB FIFO DRIVER (UF.ASM)
 FIFO_BASE	.EQU	$0C		; UF: REGISTERS BASE ADR
 ;
 SN76489ENABLE	.EQU	FALSE		; SN: ENABLE SN76489 SOUND DRIVER
+SN76489CHNOUT	.EQU	SNCHAN_BOTH	; SN: CHANNEL OUTPUTS: SNCHAN_[BOTH|LEFT|RIGHT]
 AUDIOTRACE	.EQU	FALSE		; ENABLE TRACING TO CONSOLE OF SOUND DRIVER
 SN7CLK		.EQU	3579545		; SN: PSG CLOCK FREQ, ASSUME MSX STD
 SNMODE		.EQU	SNMODE_VGM	; SN: DRIVER MODE: SNMODE_[NONE|RC|VGM]
diff --git a/Source/HBIOS/cfg_nabu.asm b/Source/HBIOS/cfg_nabu.asm
index 754bce99..526d6632 100644
--- a/Source/HBIOS/cfg_nabu.asm
+++ b/Source/HBIOS/cfg_nabu.asm
@@ -320,6 +320,7 @@ PIO_SBC		.EQU	FALSE		; PIO: ENABLE PARALLEL PORT DRIVER FOR 8255 CHIP
 UFENABLE	.EQU	FALSE		; UF: ENABLE ECB USB FIFO DRIVER (UF.ASM)
 ;
 SN76489ENABLE	.EQU	FALSE		; SN: ENABLE SN76489 SOUND DRIVER
+SN76489CHNOUT	.EQU	SNCHAN_BOTH	; SN: CHANNEL OUTPUTS: SNCHAN_[BOTH|LEFT|RIGHT]
 AUDIOTRACE	.EQU	FALSE		; ENABLE TRACING TO CONSOLE OF SOUND DRIVER
 SN7CLK		.EQU	3579545		; SN: PSG CLOCK FREQ, ASSUME MSX STD
 SNMODE		.EQU	SNMODE_RC	; SN: DRIVER MODE: SNMODE_[NONE|RC|VGM]
diff --git a/Source/HBIOS/cfg_rcez80.asm b/Source/HBIOS/cfg_rcez80.asm
index 2b124873..c36f6efc 100644
--- a/Source/HBIOS/cfg_rcez80.asm
+++ b/Source/HBIOS/cfg_rcez80.asm
@@ -336,6 +336,7 @@ PIO_SBC		.EQU	FALSE		; PIO: ENABLE PARALLEL PORT DRIVER FOR 8255 CHIP
 UFENABLE	.EQU	FALSE		; UF: ENABLE ECB USB FIFO DRIVER (UF.ASM)
 ;
 SN76489ENABLE	.EQU	FALSE		; SN: ENABLE SN76489 SOUND DRIVER
+SN76489CHNOUT	.EQU	SNCHAN_LEFT	; SN: CHANNEL OUTPUTS: SNCHAN_[BOTH|LEFT|RIGHT]
 AUDIOTRACE	.EQU	FALSE		; ENABLE TRACING TO CONSOLE OF SOUND DRIVER
 SN7CLK		.EQU	3579545		; SN: PSG CLOCK FREQ, ASSUME MSX STD
 SNMODE		.EQU	SNMODE_RC	; SN: DRIVER MODE: SNMODE_[NONE|RC|VGM]
diff --git a/Source/HBIOS/cfg_rcz180.asm b/Source/HBIOS/cfg_rcz180.asm
index b229fbb0..34341f3c 100644
--- a/Source/HBIOS/cfg_rcz180.asm
+++ b/Source/HBIOS/cfg_rcz180.asm
@@ -321,6 +321,7 @@ PIO_SBC		.EQU	FALSE		; PIO: ENABLE PARALLEL PORT DRIVER FOR 8255 CHIP
 UFENABLE	.EQU	FALSE		; UF: ENABLE ECB USB FIFO DRIVER (UF.ASM)
 ;
 SN76489ENABLE	.EQU	FALSE		; SN: ENABLE SN76489 SOUND DRIVER
+SN76489CHNOUT	.EQU	SNCHAN_BOTH	; SN: CHANNEL OUTPUTS: SNCHAN_[BOTH|LEFT|RIGHT]
 AUDIOTRACE	.EQU	FALSE		; ENABLE TRACING TO CONSOLE OF SOUND DRIVER
 SN7CLK		.EQU	3579545		; SN: PSG CLOCK FREQ, ASSUME MSX STD
 SNMODE		.EQU	SNMODE_RC	; SN: DRIVER MODE: SNMODE_[NONE|RC|VGM]
diff --git a/Source/HBIOS/cfg_rcz280.asm b/Source/HBIOS/cfg_rcz280.asm
index 8d9da62b..a496f52c 100644
--- a/Source/HBIOS/cfg_rcz280.asm
+++ b/Source/HBIOS/cfg_rcz280.asm
@@ -325,6 +325,7 @@ PIO_SBC		.EQU	FALSE		; PIO: ENABLE PARALLEL PORT DRIVER FOR 8255 CHIP
 UFENABLE	.EQU	FALSE		; UF: ENABLE ECB USB FIFO DRIVER (UF.ASM)
 ;
 SN76489ENABLE	.EQU	FALSE		; SN: ENABLE SN76489 SOUND DRIVER
+SN76489CHNOUT	.EQU	SNCHAN_BOTH	; SN: CHANNEL OUTPUTS: SNCHAN_[BOTH|LEFT|RIGHT]
 AUDIOTRACE	.EQU	FALSE		; ENABLE TRACING TO CONSOLE OF SOUND DRIVER
 SN7CLK		.EQU	3579545		; SN: PSG CLOCK FREQ, ASSUME MSX STD
 SNMODE		.EQU	SNMODE_RC	; SN: DRIVER MODE: SNMODE_[NONE|RC|VGM]
diff --git a/Source/HBIOS/cfg_rcz80.asm b/Source/HBIOS/cfg_rcz80.asm
index a3069384..8942e3a0 100644
--- a/Source/HBIOS/cfg_rcz80.asm
+++ b/Source/HBIOS/cfg_rcz80.asm
@@ -320,6 +320,7 @@ PIO_SBC		.EQU	FALSE		; PIO: ENABLE PARALLEL PORT DRIVER FOR 8255 CHIP
 UFENABLE	.EQU	FALSE		; UF: ENABLE ECB USB FIFO DRIVER (UF.ASM)
 ;
 SN76489ENABLE	.EQU	FALSE		; SN: ENABLE SN76489 SOUND DRIVER
+SN76489CHNOUT	.EQU	SNCHAN_BOTH	; SN: CHANNEL OUTPUTS: SNCHAN_[BOTH|LEFT|RIGHT]
 AUDIOTRACE	.EQU	FALSE		; ENABLE TRACING TO CONSOLE OF SOUND DRIVER
 SN7CLK		.EQU	3579545		; SN: PSG CLOCK FREQ, ASSUME MSX STD
 SNMODE		.EQU	SNMODE_RC	; SN: DRIVER MODE: SNMODE_[NONE|RC|VGM]
diff --git a/Source/HBIOS/cfg_rph.asm b/Source/HBIOS/cfg_rph.asm
index 2ecbb855..b866b733 100644
--- a/Source/HBIOS/cfg_rph.asm
+++ b/Source/HBIOS/cfg_rph.asm
@@ -271,6 +271,7 @@ UFENABLE	.EQU	FALSE		; UF: ENABLE ECB USB FIFO DRIVER (UF.ASM)
 FIFO_BASE	.EQU	$0C		; UF: REGISTERS BASE ADR
 ;
 SN76489ENABLE	.EQU	FALSE		; SN: ENABLE SN76489 SOUND DRIVER
+SN76489CHNOUT	.EQU	SNCHAN_BOTH	; SN: CHANNEL OUTPUTS: SNCHAN_[BOTH|LEFT|RIGHT]
 AUDIOTRACE	.EQU	FALSE		; ENABLE TRACING TO CONSOLE OF SOUND DRIVER
 SN7CLK		.EQU	3579545		; SN: PSG CLOCK FREQ, ASSUME MSX STD
 SNMODE		.EQU	SNMODE_NONE	; SN: DRIVER MODE: SNMODE_[NONE|RC|VGM]
diff --git a/Source/HBIOS/cfg_s100.asm b/Source/HBIOS/cfg_s100.asm
index 14e2225a..92d7829c 100644
--- a/Source/HBIOS/cfg_s100.asm
+++ b/Source/HBIOS/cfg_s100.asm
@@ -305,6 +305,7 @@ PIO_SBC		.EQU	FALSE		; PIO: ENABLE PARALLEL PORT DRIVER FOR 8255 CHIP
 UFENABLE	.EQU	FALSE		; UF: ENABLE ECB USB FIFO DRIVER (UF.ASM)
 ;
 SN76489ENABLE	.EQU	FALSE		; SN: ENABLE SN76489 SOUND DRIVER
+SN76489CHNOUT	.EQU	SNCHAN_BOTH	; SN: CHANNEL OUTPUTS: SNCHAN_[BOTH|LEFT|RIGHT]
 AUDIOTRACE	.EQU	FALSE		; ENABLE TRACING TO CONSOLE OF SOUND DRIVER
 SN7CLK		.EQU	3579545		; SN: PSG CLOCK FREQ, ASSUME MSX STD
 SNMODE		.EQU	SNMODE_RC	; SN: DRIVER MODE: SNMODE_[NONE|RC|VGM]
diff --git a/Source/HBIOS/cfg_sbc.asm b/Source/HBIOS/cfg_sbc.asm
index 6da370f0..c6c8ed23 100644
--- a/Source/HBIOS/cfg_sbc.asm
+++ b/Source/HBIOS/cfg_sbc.asm
@@ -271,6 +271,7 @@ UFENABLE	.EQU	FALSE		; UF: ENABLE ECB USB FIFO DRIVER (UF.ASM)
 UFBASE		.EQU	$0C		; UF: REGISTERS BASE ADR
 ;
 SN76489ENABLE	.EQU	FALSE		; SN: ENABLE SN76489 SOUND DRIVER
+SN76489CHNOUT	.EQU	SNCHAN_BOTH	; SN: CHANNEL OUTPUTS: SNCHAN_[BOTH|LEFT|RIGHT]
 AUDIOTRACE	.EQU	FALSE		; ENABLE TRACING TO CONSOLE OF SOUND DRIVER
 SN7CLK		.EQU	3579545		; SN: PSG CLOCK FREQ, ASSUME MSX STD
 SNMODE		.EQU	SNMODE_VGM	; SN: DRIVER MODE: SNMODE_[NONE|RC|VGM]
diff --git a/Source/HBIOS/cfg_scz180.asm b/Source/HBIOS/cfg_scz180.asm
index 018029b9..b334a783 100644
--- a/Source/HBIOS/cfg_scz180.asm
+++ b/Source/HBIOS/cfg_scz180.asm
@@ -315,6 +315,7 @@ PIO_SBC		.EQU	FALSE		; PIO: ENABLE PARALLEL PORT DRIVER FOR 8255 CHIP
 UFENABLE	.EQU	FALSE		; UF: ENABLE ECB USB FIFO DRIVER (UF.ASM)
 ;
 SN76489ENABLE	.EQU	FALSE		; SN: ENABLE SN76489 SOUND DRIVER
+SN76489CHNOUT	.EQU	SNCHAN_BOTH	; SN: CHANNEL OUTPUTS: SNCHAN_[BOTH|LEFT|RIGHT]
 AUDIOTRACE	.EQU	FALSE		; ENABLE TRACING TO CONSOLE OF SOUND DRIVER
 SN7CLK		.EQU	3579545		; SN: PSG CLOCK FREQ, ASSUME MSX STD
 SNMODE		.EQU	SNMODE_RC	; SN: DRIVER MODE: SNMODE_[NONE|RC|VGM]
diff --git a/Source/HBIOS/cfg_z80retro.asm b/Source/HBIOS/cfg_z80retro.asm
index 8fb1c216..f6f4fd1c 100644
--- a/Source/HBIOS/cfg_z80retro.asm
+++ b/Source/HBIOS/cfg_z80retro.asm
@@ -239,6 +239,7 @@ PIOSBASE	.EQU	$60		; PIO: PIO REGISTERS BASE ADR FOR SBC PPI
 UFENABLE	.EQU	FALSE		; UF: ENABLE ECB USB FIFO DRIVER (UF.ASM)
 ;
 SN76489ENABLE	.EQU	FALSE		; SN76489 SOUND DRIVER
+SN76489CHNOUT	.EQU	SNCHAN_BOTH	; SN: CHANNEL OUTPUTS: SNCHAN_[BOTH|LEFT|RIGHT]
 AY38910ENABLE	.EQU	FALSE		; AY: AY-3-8910 / YM2149 SOUND DRIVER
 SPKENABLE	.EQU	FALSE		; SPK: ENABLE RTC LATCH IOBIT SOUND DRIVER (SPK.ASM)
 ;
diff --git a/Source/HBIOS/cfg_zeta.asm b/Source/HBIOS/cfg_zeta.asm
index 0a213bb3..e35ea484 100644
--- a/Source/HBIOS/cfg_zeta.asm
+++ b/Source/HBIOS/cfg_zeta.asm
@@ -210,6 +210,7 @@ PIOSBASE	.EQU	$60		; PIO: PIO REGISTERS BASE ADR FOR SBC PPI
 UFENABLE	.EQU	FALSE		; UF: ENABLE ECB USB FIFO DRIVER (UF.ASM)
 ;
 SN76489ENABLE	.EQU	FALSE		; SN76489 SOUND DRIVER
+SN76489CHNOUT	.EQU	SNCHAN_BOTH	; SN: CHANNEL OUTPUTS: SNCHAN_[BOTH|LEFT|RIGHT]
 AY38910ENABLE	.EQU	FALSE		; AY: AY-3-8910 / YM2149 SOUND DRIVER
 SPKENABLE	.EQU	FALSE		; SPK: ENABLE RTC LATCH IOBIT SOUND DRIVER (SPK.ASM)
 ;
diff --git a/Source/HBIOS/cfg_zeta2.asm b/Source/HBIOS/cfg_zeta2.asm
index 00900b97..3a7bc05c 100644
--- a/Source/HBIOS/cfg_zeta2.asm
+++ b/Source/HBIOS/cfg_zeta2.asm
@@ -221,6 +221,7 @@ PIOSBASE	.EQU	$60		; PIO: PIO REGISTERS BASE ADR FOR SBC PPI
 UFENABLE	.EQU	FALSE		; UF: ENABLE ECB USB FIFO DRIVER (UF.ASM)
 ;
 SN76489ENABLE	.EQU	FALSE		; SN76489 SOUND DRIVER
+SN76489CHNOUT	.EQU	SNCHAN_BOTH	; SN: CHANNEL OUTPUTS: SNCHAN_[BOTH|LEFT|RIGHT]
 AY38910ENABLE	.EQU	FALSE		; AY: AY-3-8910 / YM2149 SOUND DRIVER
 SPKENABLE	.EQU	FALSE		; SPK: ENABLE RTC LATCH IOBIT SOUND DRIVER (SPK.ASM)
 ;
diff --git a/Source/HBIOS/sn76489.asm b/Source/HBIOS/sn76489.asm
index 9b5770b5..b52d0f1b 100644
--- a/Source/HBIOS/sn76489.asm
+++ b/Source/HBIOS/sn76489.asm
@@ -48,7 +48,7 @@ SN76489_PORT16_RIGHT	.EQU	(IO_SEGMENT*256) + SN76489_PORT_RIGHT
 ; For CPU @ ~18Mhz, the eZ80 must have at least 4 Bus Cycles for I/O operations
 ; For CPU @ ~24Mhz, the eZ80 must have at least 5 Bus Cycles for I/O operations
 
-SN76489_IO_DELAY	.EQU	15	; 200us DELAY BETWEEN CHANNEL WRITES
+SN76489_IO_DELAY	.EQU	5	; 200us DELAY BETWEEN CHANNEL WRITES
 
 #ENDIF
 	DEVECHO	", IO_LEFT="
@@ -116,7 +116,6 @@ SN7_VOLUME_OFF:
 	OUT	(RTCIO),A		; TO HALF CLOCK SPEED
 #ENDIF
 
-
 	LD	A, CHANNEL_0_SILENT
 	LD	BC, SN76489_PORT16_LEFT
 	EZ80_DELAY_START(SN76489_IO_DELAY, SN7_DELAY_COUNTER)
@@ -313,10 +312,13 @@ SN7_APPLY_VOL:				; APPLY VOLUME TO BOTH LEFT AND RIGHT CHANNELS
 
 	LD	BC, SN76489_PORT16_LEFT
 	EZ80_DELAY_WAIT(SN76489_IO_DELAY, SN7_DELAY_COUNTER)
+#IF ((SN76489CHNOUT == SNCHAN_BOTH) | (SN76489CHNOUT == SNCHAN_LEFT))
 	OUT	(C), A
-
+#ENDIF
+#IF ((SN76489CHNOUT == SNCHAN_BOTH) | (SN76489CHNOUT == SNCHAN_RIGHT))
 	LD	BC, SN76489_PORT16_RIGHT
 	OUT	(C), A
+#ENDIF
 
 #IFDEF SBCV2004
 	LD	A,(HB_RTCVAL)
@@ -363,10 +365,13 @@ SN7_APPLY_PRD:
 
 	LD	BC, SN76489_PORT16_LEFT
 	EZ80_DELAY_WAIT(SN76489_IO_DELAY, SN7_DELAY_COUNTER)
+#IF ((SN76489CHNOUT == SNCHAN_BOTH) | (SN76489CHNOUT == SNCHAN_LEFT))
 	OUT	(C), A
-
+#ENDIF
+#IF ((SN76489CHNOUT == SNCHAN_BOTH) | (SN76489CHNOUT == SNCHAN_RIGHT))
 	LD	BC, SN76489_PORT16_RIGHT
 	OUT	(C), A
+#ENDIF
 
 #IFDEF SBCV2004
 	LD	A,(HB_RTCVAL)
@@ -402,14 +407,15 @@ SN7_APPLY_PRD:
 	POP	AF
 #ENDIF
 
-	EZ80_DELAY_WAIT(SN76489_IO_DELAY, SN7_DELAY_COUNTER)
-
 	LD	BC, SN76489_PORT16_LEFT
 	EZ80_DELAY_WAIT(SN76489_IO_DELAY, SN7_DELAY_COUNTER)
+#IF ((SN76489CHNOUT == SNCHAN_BOTH) | (SN76489CHNOUT == SNCHAN_LEFT))
 	OUT	(C), A
-
+#ENDIF
+#IF ((SN76489CHNOUT == SNCHAN_BOTH) | (SN76489CHNOUT == SNCHAN_RIGHT))
 	LD	BC, SN76489_PORT16_RIGHT
 	OUT	(C), A
+#ENDIF
 
 #IFDEF SBCV2004
 	LD	A,(HB_RTCVAL)
diff --git a/Source/HBIOS/std.asm b/Source/HBIOS/std.asm
index 3a90169d..805c8d42 100644
--- a/Source/HBIOS/std.asm
+++ b/Source/HBIOS/std.asm
@@ -242,6 +242,12 @@ SNMODE_RC	.EQU	1		; RCBUS SOUND MODULE
 SNMODE_VGM	.EQU	2		; VGM ECB BOARD
 SNMODE_DUO	.EQU	3		; DUODYNE MEDIA-IO BOARD
 ;
+; SN SOUND MODULE CHANNEL SELECTION
+;
+SNCHAN_BOTH	.EQU	0		; BOTH LEFT & RIGHT CHANNELS GET SAME OUTPUT
+SNCHAN_LEFT	.EQU	1		; LEFT CHANNEL ONLY
+SNCHAN_RIGHT	.EQU	2		; RIGHT CHANNEL ONLY
+;
 ; TMS VIDEO MODE SELECTIONS
 ;
 TMSMODE_NONE	.EQU	0