Next186_SoC - load bios from MBR gap

bootstrap.diff

diff -Naur Next186_SoC.orig/186Code/BIOS/bootload_BIOS_SD/bootstrap.asm Next186_SoC/186Code/BIOS/bootload_BIOS_SD/bootstrap.asm
--- Next186_SoC.orig/186Code/BIOS/bootload_BIOS_SD/bootstrap.asm	2016-09-26 14:42:28.401003600 +0200
+++ Next186_SoC/186Code/BIOS/bootload_BIOS_SD/bootstrap.asm	2018-02-14 22:57:25.033245500 +0100
@@ -95,32 +95,29 @@
 		call		sdinit_
 		test		ax, ax
 		jz		short RS232
-		mov		dx, ax
+		mov		dx, ax		; first try to read bios from end of card
 		shr		dx, 6
 		shl		ax, 10
 		mov		cx, BIOSSIZE       ;  sectors
 		sub		ax, cx
 		sbb		dx, 0
-		xor		bx, bx       ; read BIOSSIZE/2 KB BIOS at 0f000h:0h
-nextsect:      
-		push		ax
-		push		dx
-		push		cx
-		call		sdread_
-		dec		cx
-		pop		cx
-		pop		dx
-		pop		ax
-		jnz		short RS232  ; cx was not 1
-		add		ax, 1
-		adc		dx, 0
-		add		bx, 512    
-		loop		nextsect
-		cmp		word ptr ds:[0], 'eN'
-		jne		short RS232             
-		cmp		word ptr ds:[2], 'tx'
-		je		short   BIOSOK
-
+		xor		bx, bx		; read BIOSSIZE/2 KB BIOS at 0f000h:0h
+		call		sdbiosread_
+		test		cx,cx		; all sectors read?
+		jz		short BOK	; BIOSOK label too far
+		xor		dx,dx		; now try from sector 1
+		mov		ax,1
+nextbeg:
+		mov		cx, BIOSSIZE
+		xor		bx, bx		; read BIOSSIZE/2 KB BIOS at 0f000h:0h
+		call		sdbiosread_
+		test		cx,cx		; all sectors read?
+BOK:
+		jz		short BIOSOK
+		add		ax, 1		;try next sector, typically first partiton starts at sector 63
+		adc		dx, 0		;so try to search for bios start until sector 63-BIOSSIZE
+		cmp		ax,63-BIOSSIZE
+		jne		short nextbeg
 RS232: 
 		mov		dx, 3c0h
 		mov		al, 10h
@@ -314,6 +311,41 @@
 		call		sdrb        ; 8T
 		ret     
 sdread_ endp
+
+;---------------------  read bios from sd card, check signature ----------------------
+sdbiosread_ proc near  ; DX:AX start sector, DS:BX start buffer, CX=number of sectors 
+		push		ax         ; read first sector and check bios signature
+		push		dx
+		push		cx
+		call		sdread_
+		dec		cx
+		pop		cx
+		pop		dx
+		pop		ax
+		jnz		short biosfail  ; cx was not 1  - sector reading failed
+		cmp		word ptr ds:[0], 'eN'
+		jne		short biosfail             
+		cmp		word ptr ds:[2], 'tx'
+		jne		short biosfail             
+ 		dec		cx       
+nextsect:
+		add		ax, 1             ; signature ok, read next sectors      
+		adc		dx, 0
+		add		bx, 512
+		push		ax 
+		push		dx
+		push		cx
+		call		sdread_
+		dec		cx
+		pop		cx
+		pop		dx
+		pop		ax
+		jnz		short biosfail  ; cx was not 1
+		loop		nextsect
+biosfail:    
+		ret
+sdbiosread_ endp
+
         
 ;---------------------  init SD ----------------------
 sdinit_ proc near       ; returns AX = num kilosectors
@@ -387,7 +419,7 @@
 sdinit_ endp
 
     
-booterrmsg  db  'BIOS not present on SDCard last 8KB, waiting on RS232 (115200bps, f000:100) ...', 0
+booterrmsg  db  'BIOS not found on SDHC card, waiting on RS232 (115200bps, f000:100) ...', 0
 SD_CMD0		db		40h, 0, 0, 0, 0, 95h
 SD_CMD8		db		48h, 0, 0, 1, 0aah, 087h
 SD_CMD9		db		49h, 0, 0, 0, 0, 0ffh
diff -Naur Next186_SoC.orig/186Code/BIOS/bootload_BIOS_SD/bootstrap_print.c Next186_SoC/186Code/BIOS/bootload_BIOS_SD/bootstrap_print.c
--- Next186_SoC.orig/186Code/BIOS/bootload_BIOS_SD/bootstrap_print.c	1970-01-01 01:00:00.000000000 +0100
+++ Next186_SoC/186Code/BIOS/bootload_BIOS_SD/bootstrap_print.c	2018-02-13 14:10:09.257871900 +0100
@@ -0,0 +1,35 @@
+// utility for printing the boot code in Lattice Memory Initialization format (.mem)
+
+#include <stdio.h>
+
+//use just unix line feed as original Cache_bootload.mem, \n or \r\n could possibly work too
+#define EOL "\x0a"
+
+unsigned int buf[1024];
+int main(int argc, char *argv[])
+{
+  char *infname="bootstrap.com";
+  FILE *out=stdout;
+  if (argc>1) infname=argv[1];
+  if (argc>2) out=fopen(argv[2],"wb");
+	FILE *in = fopen(infname, "rb");
+	fseek(in, 256, 0);
+	size_t sz = fread(buf, 1, sizeof(buf), in) / sizeof(int); 
+	int i;
+	// header as per Lattice Memory Initialization format (.mem) http://srecord.sourceforge.net/man/man5/srec_mem.html
+	fprintf(out,
+		"#Format=Hex" EOL
+		"#Depth=256" EOL
+		"#Width=32" EOL
+		"#AddrRadix=3" EOL
+		"#DataRadix=3" EOL
+		"#Data" EOL
+	);
+	while(i<sz)
+	{
+		fprintf(out,"%08X" EOL, buf[i]); 
+		i=i+1;
+	}
+	fclose(in);
+  if (out!=stdout) fclose(out);
+}
diff -Naur Next186_SoC.orig/186Code/BIOS/bootload_BIOS_SD/makeit.bat Next186_SoC/186Code/BIOS/bootload_BIOS_SD/makeit.bat
--- Next186_SoC.orig/186Code/BIOS/bootload_BIOS_SD/makeit.bat	2013-06-06 16:19:02.943727100 +0200
+++ Next186_SoC/186Code/BIOS/bootload_BIOS_SD/makeit.bat	2018-02-13 14:20:34.871206300 +0100
@@ -2,12 +2,15 @@
 
     if exist "bootstrap.obj" del "bootstrap.obj"
     if exist "bootstrap.com" del "bootstrap.com"
+    if exist "bootstrap.mem" del "bootstrap.mem"
 
     \masm32\bin\ml /AT /c /Fl bootstrap.asm
     if errorlevel 1 goto errasm
 
     \masm32\bin\link16 /TINY bootstrap,bootstrap.com,,,,
     if errorlevel 1 goto errlink
+    REM  i686-pc-mingw32-gcc -O3 bootstrap_print.c -o bootstrap_print
+    bootstrap_print.exe bootstrap.com bootstrap.mem
     dir "bootstrap.*"
     goto TheEnd