HC11 & Edelbrock ProFlow

[Ludis Langens]

Tom Sharpe <twsharpe at mtco.com> wrote:
> I forgot where I got them....  from a list of op codes somewhere.
>
> 7B (D) 6B (X) 186B (Y) = TIM (Test immediate to memory????)
> 75 (D) 65 (X) 1865 (Y) = EIM (same as EORA except to memory)
> 72 (D) 62(X) 1862 (Y) = OIM (same as ORAA except to memory)

Those aren't standard 68HC11 instructions.  Are you sure they are in
code?  Could it be that you disassembled a data area as if it were code?

If they are actually used as real opcodes, then Motorola is being
sneaky.  The 'HC11 is supposed to trap all illegal opcodes - thus
preventing programmers from using the interesting results of undefined
opcodes.  Moto could have added these opcodes (under the table) at some
point.  This isn't unheard of - some Intel 8085's contain some very
useful extra opcodes.

The other possibility is that Edelbrock decided to define their own
opcodes by emulating them in the illegal opcode exception handler.  This
is actually common on high end CPUs (IBM Blue Lightning (a '386 clone),
68040, 68060).  The purpose here would be for Edelbrock to save on code
size.

-- 
Ludis Langens                               ludis (at) cruzers (dot) com
Mac, Fiero, & engine controller goodies:  http://www.cruzers.com/~ludis/