Kontron PCI-AOB16/12, User Manual

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Introduction 5-3 PCI-AOB8/12 (16/12) User’s Guide
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Introduction
The PCI-AOB8/12 (16/12) DACs, timers, and digital I/O use 40 consecutive I/O addresses.
Programming the PCI-AOB8/12 (16/12) is very straightforward as there are only three operating
modes, three range-selection switches per channel, and one unique addition. The basic
operation of a digital-to-analog card is to write a 12-bit value to a digital to analog converter
(DAC) pre-load (outer) register where it is buffered and loaded by an update command to a DAC
(inner) register. Outputs of that register control a "ladder" network which produces the analog
output. The output voltage range is defined by settings of the range-selection switches for that
channel. In C:
outport(BASE+(CH*2), (Volts*4096/10)-2048);
would output "Volts" volts to channel "ch", assuming a bipolar 5V range. For other bipolar
ranges, substitute the appropriate voltage span in place of "10" in the equation. For unipolar
ranges, also remove the "-2048".
Upon power-up, or hardware reset, the DAC registers are restricted to a safe value and the card is
set in Simultaneous Update mode. Since the pre-load register is not cleared upon power-up, but
left at an undefined value, a known value must be written to the preload registers before using a
"Clear Restrict-Output-Voltage" command.
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Simultaneous Update Mode
Simultaneous Update Mode is the power-up or default mode of operation for the DAC card. When
a value is written to a DAC address, the output does not change until an output update is
commanded via a read from Base 8. (Alternatively, a read of Base A will update
the DAC registers and switch the board to Automatic Update Mode.) While in Simultaneous
Update Mode, a single read will load all DAC registers with the value waiting in the pre-load
registers, causing all outputs to be updated and changed simultaneously.
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Automatic Update Mode
Automatic Update Mode is the configuration that changes a DAC output immediately after the
high-byte of the new value is written to the DAC address. If the card is in Simultaneous Update
Mode, a read of Base 2 will change the card back to Automatic Update Mode without
updating the outputs. A read of Base A will update all outputs simultaneously and then
place the card in Automatic Update Mode.