Embedded 8088 bootup string problem - with the correct email address!

Your bootup string is a far jump to the real start of the code,

jmp far 0xf000:0

A 80x86 starts at reset at a location 16 bytes down from the very top of the memory, i.e. 0xffff:0 in an 8088.

Your problem lies probably in the tool you're using in converting the executable to ROM image: EXE2BIN.EXE is not able to locate the target position freely - it creates a monilithic chunk of binary code. The program strips the .exe file header off the exeutable and relocates any segment references in the code. This is what for it requests the segment (actually section, see later) base address.

It seems that your program size is the count of bytes in the source files - there's 64 kbytes of space in your EPROM.

It seems that your memory layout has ROM at 0xf0000 to 0xfffff and RAM from

0 upward. The code may be using the RAM as being located above the ROM area so that the address arithmetic in the 8088 wraps the addresses when addressed above the one megabyte limit. This method has the advantage of having both ROM and RAM data accessible with the same segment register as long as the total data length is belog 64 kbytes.

There's no simple instruction how to generate the far jump without knowing how the program sections (called segments in assemnler documentation - an unfortunate term to mix up with the hardware segment registers) are organised - the problem is to locate the jump at EPROM offset 0xfff0.

There are better tools to do the ROM image conversion - I have used Paradigm's Locate to create ROM images from Borland C 2.5 and 4.0 with the accompanying assemblers. The difference between EXE2BIN and Locate is that Locate is able to use several section base addresses, but EXE2BIN uses only one.

Even with the DOS tools, there is an easier way: the DEBUG utility can be used as a binary editor to patch the ROM image directly in binary format - there is indeed little sense to visit the EPROM chip just to get a patchable file.

IMHO, the easiest way may be to get a hex editor for your Windows and use it to insert the bytes.

HTH

Tauno Voipio tauno voipio @ iki fi

Some snippage...

It's pretty much the best way. You can make it look nicer by coding it like this:

db 0EAh ; far jump opcode dw vector_offset dw vector_segment

And if you have a stack, which you probably don't, this will work:

mov ax,vector_segment push ax mov ax,vector_offset push ax retf

On power-on reset, you certainly can't count on the stack segment/pointer.

vector SEGMENT para public 'vect' ASSUME cs:vector jmp far ptr ProgStart db 'Muppet Labs' vector ends

You really don't need the 'Muppet Labs', but I always slip that into EPROMs. :^P

Paradigm Locate would then arrange the segments: \pclocate\loc sign.exe PROG FE000 DATA 00100 VECT FFFF0 F FE000

(RAM at the bottom, 2764 at the top.)

This was using MASM/link to create the "exe".

--
Ron Sharp.
Object-Oriented Assembler, scary stuff!

... snip ...

He already has one, in \windows\command. It is called debug.

--
Chuck F (cbfalconer@yahoo.com) (cbfalconer@worldnet.att.net)
   Available for consulting/temporary embedded and systems.
     USE worldnet address!

Did you read the whole post? Just one paragraph earlier I recommended the DOS DEBUG (which is the thing with the Windowses). A graphical hex editor is still, IMHO, easier to use.

TV

Guilty. Sorry.

--
Chuck F (cbfalconer@yahoo.com) (cbfalconer@worldnet.att.net)
   Available for consulting/temporary embedded and systems.
     USE worldnet address!