hi pommie, thanks for the advice. i like the second option you have presented but im not sure that i could sort out the delays properly.
Would it work if i added a clock fed from the master pic...
hold data high for say 3 clock cyles to put the slaves into recieve mode, followed by the sixteen bits being clocked into the slaves. If the id matches then update the servo value on that slave, if not then ignore the packet.
and as you say an ISR can handle the servo, and would just read in the latest value stored.
I'll explain the scenario, i make digital gauges for cars, but it seems that customers want all the gauges that were analogue (speedo/revs) (yes i know there digital inside!) as a digital gauge (7 Seg), and all their digital gauges as analogue.
who knows?!?!?!?
anyway, i wanna build a central module that connects to all the sensors, then handles the digital bits, and outputs data for the analogue guages on the above mentioned bus.
ID=0 all devices respond (Will be used for power on/off signals, face illumination, and doing a self test)
ID=1 Water Temp
ID=2 Oil Temp
ID=3 Oil Pressure
ID=4 Boost
ID=5 Voltage
ID=6 Cant remember (and cant be bothered to dig out my paperwork, cos you get the idea)
ID=7 Power Reserve (Rolls Royce style power reserve eg, using 44% of available bhp)
the reason for the bus system is that you can have just one, or all 7 or any number inbetween of the gauges, and if i decide to face style, then its plug and play. i can mix and match, and add new gauges later.
thanks again