Unknown 8085 opcodes

Chuck Guzis cclist at sydex.com
Thu Jan 12 13:46:02 CST 2017

On 01/12/2017 11:21 AM, Sean Conner wrote:

>   But are there disassemblers that can handle somehing like:
> 		jsr	puts
> 		fcc	'Hello, world!',13,0
> 		clra
> 		...
> 	puts	puls	x
> 	puts1	lda	,x+
> 		beq	puts9
> 		jsr	putchar
> 		bra	puts1
> 	puts9	pshs	x
> 		rts
> I recall that being a somewhat common idiom in 8-bit code of the
> 80s.

Good question.  It wasn't just 8-bit code that did that.  When I was
churning out 8086 real-mode code, I used a somewhat amplified version of
that for debugging.  E.g.,

	DB	"At point xx, CX=#CX, AX=#AX",0

The debug print routine parsed the string and inserted the (saved)
values of the specified registers.  It could even show contents of
memory pointed to by a register as well as contents of I/O ports.  Very
useful if you didn't have an ICE handy.

I do know that IDA reverts to "unknown" mode when a byte value not
corresponding to a known opcode is presented.


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