From affc47efc2af91733495de9ed5b80d82d2cabe14 Mon Sep 17 00:00:00 2001
From: Wayne Warthen <wwarthen@gmail.com>
Date: Sat, 11 Oct 2025 15:10:58 -0700
Subject: [PATCH] Support DLP Connection on S100 Serial I/O

---
 Doc/ChangeLog.txt                |  1 +
 Source/HBIOS/Config/SZ80_std.asm |  8 ++++++++
 Source/HBIOS/hbios.asm           |  8 +++++++-
 Source/HBIOS/sser.asm            | 33 ++++++++++++++++++++++++++++++++
 Source/ver.inc                   |  2 +-
 Source/ver.lib                   |  2 +-
 6 files changed, 51 insertions(+), 3 deletions(-)

diff --git a/Doc/ChangeLog.txt b/Doc/ChangeLog.txt
index ea905135..c4932518 100644
--- a/Doc/ChangeLog.txt
+++ b/Doc/ChangeLog.txt
@@ -32,6 +32,7 @@ Version 3.6
 - HJB: Update PPIDE driver, add support for MSX BEER IDE interface
 - HJB: Added loader for MSX
 - HJB: Added IDE driver master media detect option
+- WBW: Add support for S100 Serial I/O DLP Serial connection
 
 Version 3.5.1
 -------------
diff --git a/Source/HBIOS/Config/SZ80_std.asm b/Source/HBIOS/Config/SZ80_std.asm
index 75582dc1..26685630 100644
--- a/Source/HBIOS/Config/SZ80_std.asm
+++ b/Source/HBIOS/Config/SZ80_std.asm
@@ -56,6 +56,14 @@ MEMMGR		.SET	MM_SZ80		; MEMORY MANAGER: MM_[SBC|Z2|N8|Z180|Z280|MBC|RPH|MON|EZ51
 FPLED_ENABLE	.SET	TRUE		; FP: ENABLES FRONT PANEL LEDS
 FPLED_IO	.SET	$05		; FP: PORT ADDRESS FOR FP LEDS
 ;
+SSERENABLE	.SET	TRUE		; SSER: ENABLE SIMPLE SERIAL DRIVER (SSER.ASM)
+SSERSTATUS	.SET	$AA		; SSER: STATUS PORT
+SSERDATA	.SET	$AC		; SSER: DATA PORT
+SSERIRDY	.SET	%10000000	; SSER: INPUT READY BIT MASK
+SSERIINV	.SET	TRUE		; SSER: INPUT READY BIT INVERTED
+SSERORDY	.SET	%01000000	; SSER: OUTPUT READY BIT MASK
+SSEROINV	.SET	TRUE		; SSER: OUTPUT READY BIT INVERTED
+;
 PPIDEENABLE	.SET	TRUE		; PPIDE: ENABLE PARALLEL PORT IDE DISK DRIVER (PPIDE.ASM)
 ;
 ESPSDENABLE	.SET	TRUE		; ESPSD: ENABLE S100 ESP32 SD DISK DRIVER (ESPSD.ASM)
diff --git a/Source/HBIOS/hbios.asm b/Source/HBIOS/hbios.asm
index 83f50676..45f58ec4 100644
--- a/Source/HBIOS/hbios.asm
+++ b/Source/HBIOS/hbios.asm
@@ -188,7 +188,7 @@ SUPCTS	.EQU	FALSE		; SUPPRESS CTS DURING HBIOS BOOT
 ; MBC: LED Port=0x70, bits 1-0, normal, shared w/ RTC port (LEDMODE_RTC)
 ; RPH?
 ; DUO: LED Port=0x94, bits 1-0, normal, shared w/ RTC port (LEDMODE_RTC)
-; S100: LED Port = $0E, bit 2, inverted, dedicated port (LEDMODE_SC)
+; S100 Z180 SBC: LED Port = $0E, bit 2, inverted, dedicated port (LEDMODE_SC)
 ; NABU: LED Port = $00, bits 5-3, normal, shared w/ control port (LEDMODE_NABU)
 ;
 #IF (LEDENABLE)
@@ -3702,6 +3702,12 @@ HB_WDZ:
 	AND	%00000001		; ISOLATE CONSOLE BIT
 	JR	NZ,INITSYS3		; NOT SET, BYPASS CONSOLE SWITCH
   #ENDIF
+;
+  #IF ((PLATFORM == PLT_SZ80) & (MEMMGR == MM_SZ80))
+	IN	A,($EF)			; GET IO BYTE
+	AND	%00100000		; ISOLATE CONSOLE BIT
+	JR	Z,INITSYS3		; IF ZERO, BYPASS CONSOLE SWITCH
+  #ENDIF
 ;
   #IF ((PLATFORM == PLT_SZ80) & (MEMMGR == MM_Z2))
 	; IOBYTE: XXXXXVVC
diff --git a/Source/HBIOS/sser.asm b/Source/HBIOS/sser.asm
index 726b83e7..93d8669c 100644
--- a/Source/HBIOS/sser.asm
+++ b/Source/HBIOS/sser.asm
@@ -13,6 +13,15 @@
 ;
 SSER_PREINIT:
 ;
+; TEST FOR PRESENCE
+;
+	XOR	A			; CLEAR ACCUM
+	LD	(SSER_PRESENT),A	; PRESET TO NOT PRESENT
+	CALL	SSER_DETECT		; CHECK FOR HARDWARE, Z=PRESENT
+	RET	NZ			; ABORT IF NOT PRESENT
+	OR	$FF			; PRESENT FLAG
+	LD	(SSER_PRESENT),A	; STORE IT
+;
 ; ADD OURSELVES TO CIO DISPATCH TABLE
 ;
 	LD	D,0			; PHYSICAL UNIT IS ZERO
@@ -26,6 +35,9 @@ SSER_PREINIT:
 ;
 ;
 SSER_INIT:
+	LD	A,(SSER_PRESENT)	; PRESENT FLAG
+	OR	A			; SET FLAGS
+	RET	Z			; ABORT IF NOT PRESENT
 	CALL	NEWLINE
 	PRTS("SSER:$")
 	PRTS(" IO=0x$")			; FORMATTING
@@ -114,3 +126,24 @@ SSER_DEVICE:
 	LD	L,SSERSTATUS		; L := BASE I/O ADDRESS
 	XOR	A			; SIGNAL SUCCESS
 	RET
+;
+; TEST FOR HARDWARE PRESENCE BY CHECKING THE STATUS PORT.  IF IT IS
+; $FF, WE ASSUME NOT PRESENT.  THEN READ PORT A DIFFERENT WAY.  IF
+; PRESENT PORT SHOULD HAVE SAME VALUE.
+; 
+;
+SSER_DETECT:
+	IN	A,(SSERSTATUS)		; GET DATA PORT VALUE DIRECTLY
+	CP	$FF			; CHECK FOR $FF
+	JR	NZ,SSER_DETECT1		; IF NOT $FF, MAY BE ACTIVE, CONTINUE
+	OR	A			; SWITCH ZF BACK TO NZ
+	RET				; DONE
+SSER_DETECT1:
+	LD	C,SSERSTATUS		; PORT ADR TO C
+	IN	B,(C)			; GET DATA PORT VALUE VIA (C)
+	CP	B			; COMPARE, EQUAL IMPLIES ACTIVE PORT
+	RET
+;
+;
+;
+SSER_PRESENT	.DB	0		; FLAG FOR HARDWARE PRESENT
\ No newline at end of file
diff --git a/Source/ver.inc b/Source/ver.inc
index 8926ee02..2a8d9914 100644
--- a/Source/ver.inc
+++ b/Source/ver.inc
@@ -2,7 +2,7 @@
 #DEFINE	RMN	6
 #DEFINE	RUP	0
 #DEFINE	RTP	0
-#DEFINE BIOSVER	"3.6.0-dev.32"
+#DEFINE BIOSVER	"3.6.0-dev.33"
 #define rmj	RMJ
 #define rmn	RMN
 #define rup	RUP
diff --git a/Source/ver.lib b/Source/ver.lib
index 306eaa19..3502ac45 100644
--- a/Source/ver.lib
+++ b/Source/ver.lib
@@ -3,5 +3,5 @@ rmn	equ	6
 rup	equ	0
 rtp	equ	0
 biosver	macro
-	db	"3.6.0-dev.32"
+	db	"3.6.0-dev.33"
 	endm