Mike, you need to provide a chip-select for each device on the SPI bus.
I've found that it's much easier to do the SPI bus in software as many
devices, such as 12-Bit converters, require more overhead with a hardware
SPI bus.

   - Tom

At 10:50 AM 4/20/99 +0100, Michael Rigby-Jones wrote:
>I call upon the mighty piclist once more....
>
>I've just been asked if I can help with a project involving a dual 12 bit
>DAC (MAX144) and a dual 12 bit ADC (MAX5156) which are to be part of a
>closed loop control system.  The system has to have  very fast response time
>and the sampling speed will need to be in the region of 50k samples/sec.
>This means I will need a part with a built in SPI interface.  No problem as
>we have an emulator for the 16C63 etc.
>
>However, this system is to be controlled via a 68HC12 over an SPI bus.
>Hmmm.  Now do any parts have 2 SPI interfaces?  Because I think that's what
>I'm going to need unfortunately.  The PIC will (I suspect) be running pretty
>well flat out performing it's control functions so a software implementation
>is going to be tricky.
>
>Any suggestions?
>
>Regards
>
>Mike Rigby-Jones