AD1200 Reference
Introduction
The Analogue To Digital Converter.
_______________________________
The AD1200 series of cards use two completely
independent Burr Brown DAC667 D/A converters.
The D/A converter takes a 12 bit digital input code and
turns it into an analogue output voltage.
Each DAC can be configured for unipolar, positive only,
0~10V and 0~5V outputs or bipolar, negative and positive,
±
10V,
±
5V and
±
2.5V outputs.
D/A Programmed I/O.
____________________
The D/A conversion are usually performed using
programmed i/o, the 12 bit output is written lower 8 bits first to
the DACLO register and then the upper 4 bits to the DACHI
register. When the DACHI register is written the digital to
analogue conversion takes place.
D/A Interrupts and DMA.
AD1200 Card Only.
_______________________
_________________
_
The AD1200 card only has the ability to use interrupt
driven or DMA outputs modes to the D/A converters.
i)
The mode bits in the ADCSR, A/D Control Status
Register, register 0, should be set to 01, 02 or 03, ie Mode
1, 2 or 3.
This stops the pacer clock if it is running.
ii)
The XMODE bits in the TIMER register is set to either to
40 hex to select DAC0 or 80 hex to select DAC1 as the
recipient of the interrupt or DMA data, at the same time,
the pacer clock source and divisor is selected, determining
the frequency of the pacer clock strobes.
iii)
The initial DAC data values are written to DACLO and
DACHI. Writing to the DACLO or DACHI registers does
not cause a D/A conversion when the extended mode bits
are set to 40 or 80 hex. Instead the conversion is caused
by the strobe signals from the pacer clock.
iv)
A write to the ADGCR register or an negative edge on the
external trigger input starts the pacer clock as selected by
the ADCSR Mode bits.
v)
DAC conversion strobes will be automatically generated by
Page 20
Chapter 1
