Just an additional note I used the LTC1453 DAC and it was easy to use and worked great I used it to drive an analog devices 4-20mA convertor chip.

hope this is of some use to somebody.

thanks again for all your help and patience

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'
'LTC1453 DAC Setup
output portC.5 'clock pin
output portA.2 'data pin
output portA.3 'CS/Load pin low to enable clock high to load data to dac output
symbol DCK = portc.5
symbol DDA = portb.0
symbol DCS = porta.2
DAOut var word ' daoutput variable
DAspan var word ' Da span adjust variable
Volt1 var word ' Raw data variable
' ----------------------------------------------------------------------------
' Get Load Value and output to DAC 0-2.5 vdc for range of 12 bits
' ----------------------------------------------------------------------------
DAC1: low DCS
DAout = volt1*DAspan ' voltage output raw signal scaling
DAout = div32 1000

shiftout DDA,DCK,1,[DAout\12]
HIgh DCS
return