disassembly of 6803 code

[Nigel Duckworth]

Arnaud wrote:

> So to determine the peripheral addresses I would have to check the
> peripheral specs?

Sort of, the peripherals can be mapped anywhere (chosen by the designer), in 
the past I have produced my own map of someone else's system but only by using 
their circuit diagram.
You could produce a circuit from your ECU (if all of the devices are 
identifiable)
but it would be very tedious.

If you have a circuit diagram then start at the chip enable pin(s) of the 
peripheral you are interested in, e.g. timer, then work back to the address 
decoder to which it is wired (74LS138, 139 etc.).
See which address lines are decoded by this chip then using the binary 
weighting of each address line calculate the unique address (or range of 
addresses) for the peripheral.
A data sheet for the address decoder would be useful.

Hope this helps.

Nigel


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