Kontron 104-AD128, User Manual

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104-ADIO128 (AD128) User’s Guide
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Using the Digital to Analog
Converters
This circuit is based on the Analog Devices AD5343 chip. Please refer to file AD53xx.pdf in the
\CHIPDOCS directory. A conversion begins after the most significant byte (of which only the
lower 4 bits will be used) has been written to a DAC. The input coding to the DACs are straight
binary. Discounting offset and gain errors, the output voltage is given by
V
out
3 (Gain * V
ref
* D_4096) + Offset
where V
ref
= 4.096V and D = the decimal equivalent of the binary code written to the DAC (a
number between 0 and 4095).
On power-up, the output values will be at the most negative for the selected range.
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Using Counter 1 to Trigger A/D and
D/A Conversions
In Mode 2 the Counter/Timer chip will generate a 2 microsecond negative going pulse at a
programmed rate. If bit 1 of the Timer-Triggered Conversion Enables register (base a
16h) is set high, the ADC chip will initiate conversions on the tick. If bit 0 is set high the DAC chip
will initiate conversions on the tick.
The ADC chip needs a command byte to begin a conversion. This byte is stored in the ADC
Command register at base + 15h. Note that only the lowest 5 bits are significant, the top 3 bits
will automatically be zeros.
Range 0-5V 0-10V ±
5V
±
10V
Gain
1.22 2.44 2.44 4.88
Offset 0V 0V -5V -10V