ADLINK ACL-8112 Series - Manual (Page 53)

Operation Theory
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5.2 D/A Conversion
The operation of the D/A conversion is simpler than the A/D operation. You
only need to write the digital values into the D/A data registers and the
corresponding voltage will be outputted through AO1 or AO2. Refer to
section 4.9 for information about the D/A data registers. The mathematical
relationship between the digital number DAn and the output voltage is
formulated as follows:
Vout Vref
DAn
= − ×
4096
where Vref is the reference voltage, Vout is the output voltage, and DAn is
the digital value in the D/A data registers.
Before performing the D/A conversion, users should be aware of the D/A
reference voltage which is set by JP1, JP2 and JP3. Please refer to section
2.11 for jumper setting. The reference voltage will effect the output voltage. If
the reference voltage is -5V, the D/A output scaling will be 0~5V. If the
reference voltage is -10V, the D/A output scaling will be 0~10V.
Note that the D/A registers are "double buffered", so that the D/A analog
output signals will not be updated until the high byte is written. When writing
12-bit data to the D/A registe rs, the low byte must be written to first before
the high byte. This procedure will ensure a single step transition for a D/A
conversion.
5.3 Digital Input and Output
To program the digital I/O operation is fairly straight forward. The digital input
operation just reads data from its corresponding registers, and the digital
output operation just writes data to its corresponding registers. The digital I/O
registers are shown in section 4.9. Note that the DIO data channel can only
be read or written in forms of 8-bits. It is impossible to access individual bits.