Mixed signal simulation (w/ external programs)

Hello!

I would like to know if it is possible to link external digital/processor  
simulators into gnucap.
In particular, I am interested in interfacing simulavr
[http://savannah.nongnu.org/projects/simulavr]
and gnucap. Simulavr is a simulator for the 8-bit AVR cpu which is very 
popular amongst hobbyists.

Is this possible at all?

If it is... how would one interface these two applications?
For my purposes, it would be acceptable to have the outputs of the MCU as 
voltage sources in gnucap and voltage probes in gnucap as inputs to the MCU 
(no modeling of current through the MCU).
For example, I would like to simulate direct digital synthesis with the MCU 
but have the analog part (ADC) be modeled also. Only looking at vector output 
files doesn't tell one too much about the final piece of electronics :)

I suppose that the most difficult part would probably linking the differential 
equation solver "clock" (transient mode time steps) of gnucap with the 
simulator clock of such a digital simulator. Maybe it would be possible to 
create a driver that runs both gnucap and simulavr (or another digital 
simulator) and exchanges signals at "intersection" points?

I really consider implementing such a thing if one could give me some advice.

Best regards,

Onno Kortmann