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BUF20800/20820EVM Software Overview
5.2.4
Write DAC Button
The method used to write the values in the DAC/V
COM
registers is based on whether or not the Auto Write
feature is enabled. The BUF20800/20820 has two methods of writing information into the DAC/V
COM
registers. The first method allows for the output voltage to change immediately after the writing to the DAC
register. In the BUF20800/20820EVM software, this mode is configured by enabling the Auto Write feature
found in the Buffer Menu dropdown menu. In this mode, as an individual channel is written to, the output
voltage changes as soon as the user moves to a different text box in the software. The second method of
writing to the DAC/V
COM
registers allows for the user to write multiple channels and then have all of the
output voltages change at the same time, rather than each channel voltage changing as soon as it is
written to.
Disabling the Auto Write feature in the software allows the user to enter all of the values desired for all of
the channels and then press the Write DAC button to change all of the output voltage of all of the
channels at one time. When the Auto Write feature is enabled, no change occurs to the output voltages
when the Write DAC button is pressed. No change occurs because after the text box for a given channel
has been updated, as soon as another item in the software is clicked, the Auto Write feature automatically
performs a write command to the updated channel that then updates the output voltage. When in the Auto
Write enabled mode, the Write DAC button cannot be pressed with different data in the corresponding
channel text boxes than the values already stored in the DAC/V
COM
register; thus, no change occurs.
shows the location in the Buffer Menu showing the Auto Write feature enabled. Clicking on the
Auto Write feature again enables/disables the feature, depending on its current state.
Figure 19. Auto Write Feature Enabled
5.2.5
Reset Button
Pressing the Reset button in the BUF20800/20820EVM software performs two functions. The first function
is to call a General-Call Reset for the BUF20800 or BUF20820. The status of the DAC/V
COM
registers after
this General-Call Reset has been used depends on the DUT on the EVM.
If the BUF20800 is in the test board, the channel registers default to 1000000000, or mid-supply.
If the BUF20820 is in the test board, the status of the DAC/V
COM
registers after this General-Call Reset
depends on whether or not the OTP has been programmed. If the OTP has been programmed, the
channel registers are loaded with the last values programmed into the OTP memory. If the OTP memory
has not been programmed, the channel registers will default to 1000000000, or mid-supply.
The second function performed after the reset button is pressed is that a Read DAC call is made to
update the corresponding channel text boxes to the current value for each channel. This function is valid
for both the BUF20800 and the BUF20820 device.
21
SBOU100 – April 2011
BUF20800/20820EVM User Guide and Software Tutorial
© 2011, Texas Instruments Incorporated