User`s guide

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Operation Theory
4.2 Analog Output Status Register
The DAC uses a series bus architecture hence there is a delay in the output
of the digital value. The data transfer time for every DA data write takes 16µs,
therefore the software driver must wait for 16µs before sending another set of
data to any analog output port. While the DA value is sending, the
Data_Send bit is
‘
H
’
. The software driver should check this bit before writing
any data to the output port. This register is read only.
Base D16~D1 D0
0x00 X Data_Send
4.3 Current Output and Range Control
A precision voltage-to-current converter XTR110 implements the current
output. The current output channel n (An) is control by the voltage of channel
n (Vn). A block diagram of the current output channels is shown in Fig 4.1.
XTR110
50 Ohm
On Board +15V
Vn
An
External Load
(Resister R
L
= 250 Ohm typical)
A.GND
Io
Current Output
Range Control
Figure 4.1 Current output circuit
The PCI-6308A provides an on board +15V power supply. Each current
output channel is a current source, which is controlled by the voltage of the
corresponding voltage output channel. For example, voltage output channel
3 control the current source of channel 3.
The output current range is programmable. The current range control
register controls all 8 current channels on the PCI-6308A. There are three
kinds of output current ranges. Refer to the following table and Section 5.2.9
for programming the current range using the
_6308_I2V_Control
function.