Analog Output Register Group - National Instruments DAQ AT-MIO-16X User Manual

Analog Output Register Group

© National Instruments Corporation
The two registers making up the Analog Output Register Group access
the two analog output channels. Data can be transferred to the DACs in
one of three ways depending on the mode configuration in Command
Register 4 according to Table 4-6. Data can be directly sent to the DACs
from the local data bus, buffered from the local bus by the DAC FIFOs,
or received serially from the AT-DSP2200 across the RTSI bus. There
are two methods of updating the DACs, immediate and posted. In the
immediate update mode, data transferred to the DACs is not buffered,
and is immediately converted to the appropriate voltage at the output.
In the posted update mode, data is converted to an output voltage only
after a falling edge is detected on the TMRTRIG* signal, or the DAC
Update Register is strobed. In the immediate update mode and the serial
mode, the DAC FIFOs are not utilized. In all other output modes, the
DAC FIFOs are used.
The output voltage generated from the digital code depends on the
configuration, unipolar or bipolar, of the associated analog output
channel. This configuration is determined by control bits in the
Command Register 2. Configuration bits in Command Register 2
determine if the digital code written to the DACs is in straight binary
form or in a two's complement form. Table 4-10 shows the output
voltage versus digital code for a unipolar analog output configuration.
Table 4-11 shows the voltage versus digital code for a bipolar analog
output configuration.
The formula for the voltage output versus digital code for a unipolar
analog output configuration is as follows:
V = V * (digital code)
out ref
where V is the reference voltage applied to the analog output channel.
ref
The digital code in the above formula is a decimal value ranging from
0 to 65,535.
Chapter 4
65,536
4-41
Register Map and Descriptions
AT-MIO-16X User Manual