BIOS V1.0

Page zero cell $1A buffered

System/BIOS.ASM

@@ -11,8 +11,9 @@
 ;V0.7	13.09.23	no IRQs
 ;V0.8	14.01.24	error correction
 ;V0.9	25.04.24	$FC & $FD buffered
+;V1.0	29.04.24	$1A buffered
 
-VERSION	= $09		;VERSION NUMBER
+VERSION	= $10		;VERSION NUMBER
 
 ;FORMAT	SD	1024 KBYTES/DISK
 
@@ -51,6 +52,8 @@ ROM_MONITOR = $E000	;Monitor cold start
 BREAKC	= $03		;BREAK CODE
 CLS	= $0C		;CLEAR SCREEN
 
+BIT_ABS	= $2C		;code byte BIT ABS
+
 ;ERROR CODES
 
 INVDRV	= $F9		;invalid drive
@@ -164,15 +167,11 @@ CONST1	CLC
 
 CONIN	JSR PUSHIOB
 	JSR ROM_CONIN
-	PHA
 	JSR PULLIOB
-	PLA
 	RTS
 
 
-CONOUT	PHA
-	JSR PUSHIOB
-	PLA
+CONOUT	JSR PUSHIOB
 	JSR ROM_CONOUT
 	JSR PULLIOB
 	RTS
@@ -218,7 +217,8 @@ SETTRK	LDA #$FB		;Sector not found
 	RTS
 
 
-READ	JSR SETLBA		;SET LBA = IMGTAB + SECS/2
+READ	JSR PUSH_E0
+	JSR SETLBA		;SET LBA = IMGTAB + SECS/2
 	BCS SD_RDX
 	JSR CHKBLK		;CHECK IF BLOCK VALID
 	BCC SD_RD1
@@ -232,23 +232,25 @@ SD_RD2	LDA BLKBUF,Y
 	STA (DMAV),Y
 	INY
 	BNE SD_RD2
-	CLC
-	RTS
+	BEQ SD_RD5
 
 SD_RD3	LDA BLKBUF+256,Y
 	STA (DMAV),Y
 	INY
 	BNE SD_RD3
+SD_RD5	JSR PULL_E0
 	CLC
 	RTS
 
 SD_RD4	JSR SD_INIT		;on error retry
 	BCS READ
+	JSR PULL_E0
 	SEC
 SD_RDX	RTS
 
 
-WRITE	JSR SETLBA		;WRITE SD card
+WRITE	JSR PUSH_E0
+	JSR SETLBA		;WRITE SD card
 	BCS SD_RDX
 	JSR CHKBLK
 	BCC SD_WR1
@@ -278,13 +280,16 @@ SD_WR4	LDA #$80
 	CMP #SYS+DIRSCS		
 	BCS SD_WR5
 	JSR SD_WB		;then write SD block immediate
+	JSR PULL_E0
 	RTS
 
-SD_WR5	CLC
+SD_WR5	JSR PULL_E0
+	CLC
 	RTS
 
 SD_WRE	JSR SD_INIT		;on error 1 retry
 	BCS WRITE
+	JSR PULL_E0
 	SEC
 	RTS
 
@@ -392,13 +397,9 @@ S_READ	BIT LBA_F		;SD_READ
 	BPL S_READ1		;if buffer dirty
 	JSR S_SAVE		;SAVE SD_BUFFER
 	BCS S_READX
-S_READ1	JSR PUSH_E0
-	JSR PUSHIOB
-	LDX #LBA		;load LBA to BLKBUF
+S_READ1	LDX #LBA		;load LBA to BLKBUF
 	LDY #LBA/256
 	JSR SD_RD_LBLK_BUF
-	JSR PULL_E0
-	JSR PULLIOB
 	BCS S_READX
 	SEC
 	RTS
@@ -408,13 +409,9 @@ S_READX	JSR SD_UPD		;UPDATE BLK/FLAG INFO
 	RTS
 
 
-S_SAVE	JSR PUSH_E0
-	JSR PUSHIOB
-	LDX #LBA_B		;save old buffer to SD
+S_SAVE	LDX #LBA_B		;save old buffer to SD
 	LDY #LBA_B/256
 	JSR SD_WR_LBLK_BUF
-	JSR PULL_E0
-	JSR PULLIOB
 	BCC S_SAVEX
 	CLC
 	RTS
@@ -423,14 +420,10 @@ S_SAVEX	SEC
 	RTS
 
 
-SD_WB	JSR PUSH_E0
-	JSR PUSHIOB
-	LDX #LBA		;Write SD_ block pysically
+SD_WB	LDX #LBA		;Write SD_ block pysically
 	LDY #LBA/256
 	JSR SD_WR_LBLK_BUF
 	BCS S_READX
-	JSR PULL_E0
-	JSR PULLIOB
 	SEC
 	RTS
 
@@ -448,58 +441,47 @@ SD_UPD	LDA LBA+3		;save LBA AND update LBA_FLAG
 	RTS
 
 
-PUSH_E0	LDX #$E3		;Save $E3..E0
-	LDY #3			;4 bytes to be saved
-PUSH_E1	LDA 0,X
-	STA E0BUF,Y
-	DEX
+PUSHIOB	STY Y_BUF
+	LDY #ZP_CELL-ZP_IOB-1	;Save page zero cells for CHR-IO
+	DB BIT_ABS
+PUSH_E0	LDY #ZP_BUF-ZP_IOB-1	;Save page zero cells
+	PHA
+PUSH_E1	LDX ZP_IOB,Y		;load page zero adr
+	LDA 0,X			;load cell content
+	STA ZP_BUF,Y		;and save it
 	DEY
 	BPL PUSH_E1
-	LDA TEMP		;save $FC
-	STA TEMPBUF
+	INY			;restore IOB
+	STY IOB
+	LDA IOBASEH
+	STA IOB+1
+	LDY Y_BUF
+	PLA
 	RTS
 
 
-PULL_E0	LDX #$E3		;Save $E3..E0
-	LDY #3			;4 bytes to be saved
-	PHA			;save A
-PULL_E1	LDA E0BUF,Y
-	STA 0,X
-	DEX
+PULLIOB	STY Y_BUF
+	LDY #ZP_CELL-ZP_IOB-1	;restore page zero cells for CHR-IO
+	DB BIT_ABS
+PULL_E0	LDY #ZP_BUF-ZP_IOB-1	;restore page zero cells
+	PHA
+	PHP
+PULL_E1	LDX ZP_IOB,Y		;load page zero adr
+	LDA ZP_BUF,Y		;load cell content
+	STA 0,X			;and restore it
 	DEY
 	BPL PULL_E1
-	LDA TEMPBUF		;restore $FC
-	STA TEMP
-	PLA			;A & C unchanged
-	RTS
-
-PUSHIOB	LDA IOB			;save $14/$15
-	STA IOBBUF
-	LDA IOB+1
-	STA IOBBUF+1
-	LDA #0
-	STA IOB
-	LDA IOBASEH
-	STA IOB+1
-	LDA YSAV		;save $FD
-	STA YSAVBUF
+	LDY Y_BUF
+	PLP
+	PLA
 	RTS
 
 
-PULLIOB	LDA IOBBUF		;restore $14/$15
-	STA IOB
-	LDA IOBBUF+1
-	STA IOB+1
-	LDA YSAVBUF		;restore $FD
-	STA YSAV
-	RTS
-
-E0BUF	DS 4,0
-TEMPBUF	DB 0
-IOBBUF	DS 2,0
-YSAVBUF	DB 0
+ZP_IOB	DB $14,$15,$FD
+ZP_CELL DB $E3,$E2,$E1,$E0,$FC,$1A
+ZP_BUF	DS ZP_BUF-ZP_IOB,0
 
-X_CNT	DB 0
+Y_BUF	DB 0
 	
 DMA