[LinuxBIOS] LPC ROM emulator [was: PLCC removal trick]

Peter Stuge stuge-linuxbios at cdy.org
Sun Sep 18 05:28:56 CEST 2005

On Thu, Sep 15, 2005 at 07:02:20AM -0700, Dave Ashley wrote:
> I looked at the FlexROM III, it appears to emulate just flat 8 or
> 16 bit devices. PLCC's are more complicated, they frequently make
> use of an LPC interface that clocks in 4 bits of data at a time (as
> I recall) to get the address into the chip, then clocks out 4 bits
> of data at a time. I think an operation is 16 bits at a time. This
> is all transparent from the system's perspective. However behind
> the scenes it is a complicated dance.

Cycles are 1, 2, 4 or 128 bytes. Required signals are 4 bit A/D bus,
cycle sync, reset and clock. Last two are same as on PCI.

LPC is a pretty neat bus. Making an emulator would be fun..

On Wed, Sep 14, 2005 at 06:44:30PM -0700, Jeff Carr wrote:
> More than that I think. How smart are these devices? Can one single
> step through instructions or dump out the registers on the CPU.(?)

I don't think so, it's only a ROM emulator, not a CPU debugger. As
for single stepping, that won't work either because the ROM has a
(very short) limited response time, it can't just block on reads.

> the capabilities of using an emulator. Man, if only someone made
> one that hooked up to gdb, then we would be in business.

I'm not sure how gdb would work with a ROM emulator, but on the other
hand I haven't done too much advanced stuff with gdb. :(

> > You will also probally need a DIP to PLCC adapter.
> Right. The adapter size is likely to be a problem. Some boards will
> not have the space to fit such an adapter. Guess it's back to the
> making adapters game.

Try to find one that builds straight up from the socket. I was using
something pretty good from ICEtech or similar when last working with
BIOS things, it didn't have the DIP size board until about an inch up
from the PLCC socket.


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