ICS Advent AOB8/16, Product Manual

Manual Number: 00650-010-6

Page 9

Chapter 5:  Programming

Programming the AOBx/16 is very straightforward as there are only two operating modes, three
sets of jumpers, and one unique addition. The basic operation of a Digital to Analog card is to write
a 16-bit value to a Digital to Analog Converter (DAC) preload register where it is buffered and
loaded with an update command to a DAC register which produces the corresponding analog out-
put (Defined by the range and polarity jumpers for that channel).

Upon power-up, or hardware reset, the DAC registers are initialized to a “zero” value and the card
is set in Simultaneous Update mode.  This ensures that upon power-up the outputs start at zero volts
out. (Note: The “I” initialize and “M” polarity mode jumpers should be set identically or the DAC
register will be initialized to the incorrect value.) Since the preload 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 an update command.

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 com-
manded via a read to the BASE+8 address. (Alternatively, a read to BASE+10 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 preload registers causing all
outputs to be updated and changed simultaneously.

Automatic Update Mode is the power-up default configuration which changes the DAC output
immediately after the new value high-byte is  written to the DAC address. If the card is in Simulta-
neous Update Mode a read to BASE+2 address will change the card back to Automatic Update
Mode without updating the outputs. Or, a read to BASE+10 will update all outputs simultaneously
and then release the card to the Automatic Update Mode.

Software Clear is a unique addition to our DAC card which resets the DAC similar to a hardware
reset without changing the operating mode. Just as a hardware reset, the zero output depends on the
proper setup of the initialize and polarity mode jumpers (See the power-up paragraph) to produce
a zero output. Since the preload registers are not cleared the previous output will be restored from
the preload register when the appropriate update command is issued to the DAC channel.