From 214182b514c282fbe723b3d6a27b378810494d2c Mon Sep 17 00:00:00 2001
From: Wayne Warthen <wwarthen@gmail.com>
Date: Tue, 21 Nov 2023 11:59:31 -0800
Subject: [PATCH] Fix RTC Initialization

When using the Z2 memory manager, if the HBIOS exceeds 16K, RTCDEFVAL will not be accessible prior to programming the Z2 memory bank registers.  In this corner case the RTC latch could be mis-programmed.  This commit introduces a workaround.
---
 Source/HBIOS/hbios.asm | 27 +++++++++++++++++++--------
 Source/ver.inc         |  2 +-
 Source/ver.lib         |  2 +-
 3 files changed, 21 insertions(+), 10 deletions(-)

diff --git a/Source/HBIOS/hbios.asm b/Source/HBIOS/hbios.asm
index ddfdfa1d..e6c0a34e 100644
--- a/Source/HBIOS/hbios.asm
+++ b/Source/HBIOS/hbios.asm
@@ -1117,12 +1117,17 @@ BOOTWAIT:
 	JR	NZ,BOOTWAIT
 #ENDIF
 ;
-;#IF ((PLATFORM == PLT_MBC) | (PLATFORM == PLT_SBC))
-	; INITIALIZE RTC LATCH BYTE
+	; EARLY RTC LATCH BYTE INITIALIZATION
 	; FOR SOME PLATFORMS THIS CONTROLS HI/LO SPEED CIRCUIT
-	LD	A,(RTCDEFVAL)		; GET DEFAULT VALUE
+	; NOTE: WE WANT TO USE (RTCDEFVAL) HERE, BUT THE Z2 MEMORY
+	; MANAGER STARTS UP WITH THE FIRST 16K OF ROM MAPPED TO ALL
+	; 4 16K BANKS OF CPU SPACE.  SO, IF RTCDEVFAL IS LOCATED AFTER
+	; PAST 16K, WE DON'T HAVE ACCESS TO IT.  FOR NOW, WE JUST USE
+	; RTCDEF WHICH IS SUBOPTIMAL, BUT PROBABLY DOES NOT CAUSE ANY
+	; PROBLEMS.
+	;LD	A,(RTCDEFVAL)		; GET DEFAULT VALUE
+	LD	A,RTCDEF		; DEFAULT VALUE
 	OUT	(RTCIO),A		; SET IT
-;#ENDIF
 ;
 #IF (PLATFORM == PLT_N8)
 	LD	A,N8_DEFACR		; ENSURE N8 ACR
@@ -1144,7 +1149,9 @@ BOOTWAIT:
 	XOR	A			; LED IS INVERTED, TURN IT ON
   #ENDIF
   #IF (LEDMODE == LEDMODE_RTC)
-	LD	A,(RTCDEFVAL)		; DEFAULT LATCH VALUE
+	; CAN'T USE (RTCDEFVAL) YET, SEE COMMENTS ABOVE
+	;LD	A,(RTCDEFVAL)		; DEFAULT LATCH VALUE
+	LD	A,RTCDEF		; DEFAULT LATCH VALUE
 	OR	%00000001		; LED 0 ON
   #ENDIF
 	OUT	(LEDPORT),A
@@ -1435,11 +1442,15 @@ S100MON_SKIP:
 	LD	A,(HB_CURBNK)		; GET HB_CURBNK
 	LD	(HBX_LOC - 2),A		; ... AND SAVE TEMP FOR APPBNK
 ;
-; THE RTCVAL FIELD OF THE PROXY DATA NEEDS TO BE INITIALIZED HERE
-; BECAUSE IT CANNOT BE PRE-INITIALIZED (SEE COMMENTS ABOVE WHERE
-; RTCVAL EQUATE IS DEFINED).
+; WE CAN NOW DO THE REAL INITIALIZATION OF THE RTC LATCH BASED ON
+; (RTCDEFVAL).  AT THIS POINT WE SHOULD HAVE ACCESS TO THE ROM LOCATION
+; WHERE RTCDEFVAL IS STORED AND THE PROXY IS INSTALLED IN UPPER RAM
+; WHERE WE WILL STORE THE WORKING SHADOW COPY (HB_RTCVAL).
+; SEE COMMENTS ABOVE REGARDING THE FUNKY WAY THAT THE RTCDEFVAL IS
+; CREATED.
 ;
 	LD	A,(RTCDEFVAL)
+	OUT	(RTCIO),A		; SET IT
 	LD	(HB_RTCVAL),A
 ;
 #IFDEF TESTING
diff --git a/Source/ver.inc b/Source/ver.inc
index 6c118fde..e2f398e9 100644
--- a/Source/ver.inc
+++ b/Source/ver.inc
@@ -2,7 +2,7 @@
 #DEFINE	RMN	4
 #DEFINE	RUP	0
 #DEFINE	RTP	0
-#DEFINE BIOSVER	"3.4.0-dev.22"
+#DEFINE BIOSVER	"3.4.0-dev.23"
 #define rmj	RMJ
 #define rmn	RMN
 #define rup	RUP
diff --git a/Source/ver.lib b/Source/ver.lib
index 70f91ac4..6c9b9eff 100644
--- a/Source/ver.lib
+++ b/Source/ver.lib
@@ -3,5 +3,5 @@ rmn	equ	4
 rup	equ	0
 rtp	equ	0
 biosver	macro
-	db	"3.4.0-dev.22"
+	db	"3.4.0-dev.23"
 	endm