Texas Instruments BUF16821EVM-USB User manual

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User's Guide
SBOU106A–May 2011–Revised May 2016
BUF16821EVM-USB Evaluation Board and Software
Tutorial
This user's guide describes the characteristics, operation, and use of the BUF16821EVM-USB evaluation
board. It discusses how to set up and configure the software and hardware, and reviews various aspects
of the program operation. Throughout this document, the terms evaluation board,evaluation module, and
EVM are synonymous with the BUF16821EVM-USB. This user's guide also includes information regarding
operating procedures and input/output connections, an electrical schematic, PCB layout drawings, and a
parts list for the EVM.
Contents
1 Overview ..................................................................................................................... 2
2 BUF16821EVM-USB Hardware Setup.................................................................................... 4
3 BUF16821EVM-USB Software............................................................................................. 7
4 BUF16821EVM-USB Software ........................................................................................... 14
5 BUF16821EVM-USB Software Overview............................................................................... 17
6 Hardware and Schematic ................................................................................................. 25
List of Figures
1 Hardware Included with BUF16821EVM-USB Kit....................................................................... 3
2 BUF16821EVM-USB Hardware Setup.................................................................................... 4
3 BUF16821EVM-USB Board Block Diagram.............................................................................. 5
4 USB_DIG_Platform Block Diagram ....................................................................................... 7
5 Typical Hardware Connections for BUF16821EVM-USB .............................................................. 8
6 Connecting External Power to the EVM.................................................................................. 9
7 Connecting the USB Cable to the USB_DIG_Platform ............................................................... 10
8 Confirmation of USB_DIG_Platform Driver Installation ............................................................... 10
9 BUF16821EVM-USB Default Jumper Settings......................................................................... 11
10 BUF16821EVM-USB Software Installation ............................................................................. 15
11 BUF16821EVM-USB License Agreements............................................................................. 16
12 BUF16821EVM-USB Software Installation Progress.................................................................. 16
13 BUF16821EVM-USB Software About Button........................................................................... 17
14 BUF16821EVM-USB Software: Communication Error with the USB_DIG_Platform.............................. 17
15 JMP5 Setting For Logic ‘1’................................................................................................ 18
16 JMP5 Setting for Logic ‘0’................................................................................................. 18
17 Measuring and Entering Power-Supply Voltage ....................................................................... 19
18 Auto Write Feature Enabled .............................................................................................. 20
19 Save to File Dialog Box Button and Window ........................................................................... 21
20 File Format of Saved Data................................................................................................ 22
21 Load From File Button and Window ..................................................................................... 23
22 Run Batch Dialog Button and Window .................................................................................. 24

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23 Control Panel Button and Window....................................................................................... 25
24 BUF16821EVM-USB Schematic......................................................................................... 26
25 BUF16821EVM-USB PCB Top Layer (Component Side) ............................................................ 27
1 Overview
The BUF16821 is a programmable gamma-voltage generator and VCOM calibrator with integrated two-bank
memory. This device offers 16 programmable gamma channels and two programmable VCOM channels,
making it ideal for 10-bit source TFT-LCD reference drivers. The BUF16821EVM-USB is a platform for
evaluating the performance of the BUF16821 under various signal, reference, and supply conditions.
This document gives a general overview of the BUF16821EVM-USB, and provides a general description
of the features and functions to be considered while using this evaluation module.

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1.1 BUF16821EVM-USB Kit Contents
Table 1 summarizes the contents of the BUF16821EVM-USB kit. Figure 1 shows all of the included
hardware. Contact the Texas Instruments Product Information Center nearest you if any component is
missing. It is highly recommended that you also check the BUF16821 product folder on the TI web site at
www.ti.com to verify that you have the latest versions of the related software.
Table 1. BUF16821EVM-USB Kit Contents
Item Quantity
BUF16821EVM-USB PCB Test Board 1
USB_DIG_Platform PCB 1
USB Cable 1
Barrel plug cable assembly 1
User’s Guide CD-ROM 1
Figure 1. Hardware Included with BUF16821EVM-USB Kit

+6V dc wall
supply
BUF16821
Test Board
Analog Supply
USB Dig Platform
Outputs Measurement
Device
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1.2 Related Documentation from Texas Instruments
The following documents provide information regarding Texas Instruments' integrated circuits used in the
assembly of the BUF16821EVM-USB. This user's guide is available from the TI web site under literature
number SBOU106. Any letter appended to the literature number corresponds to the document revision
that is current at the time of the writing of this document. Newer revisions may be available from the TI
web site, or call the Texas Instruments' Literature Response Center at [phone] or the Product
Information Center at [phone]. When ordering, identify the document by both title and literature
number.
Table 2. Related Documentation
Document Literature Number
BUF16821 Product Data Sheet SBOS428B
USB_DIG_Platform User Guide SBOU058
2 BUF16821EVM-USB Hardware Setup
Figure 2 shows the system setup for the BUF16821EVM-USB. The PC runs software that communicates
with the USB_DIG_Platform. The USB_DIG_Platform generates the analog and digital signals used to
communicate with the 16821EVM-USB. Connectors on the BUF16821EVM-USB test board allow the user
to connect to the system under test conditions and monitor the power, current, and voltage.
Figure 2. BUF16821EVM-USB Hardware Setup

BUF16821
J1
T1
TPG1
V Supply
(V Power Supply)
DUT
SD
I C Interface
2Test Outputs
I C A0 Address
Jumper
2
External Analog
Power Supply
Test Point
Header
25-Pin Male
DSUB
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2.1 Theory of Operation for BUF16821 Hardware
A block diagram of the BUF16821 test board hardware setup is shown in Figure 3. The functionality of the
PCB is such that it provides connections to the I2C™ interface and general-purpose inputs/outputs
(GPIOs) on the USB_DIG_Platform board. It also provides connection points for external connections of
the shunt voltage, bus voltage, and ground.
Figure 3. BUF16821EVM-USB Board Block Diagram

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2.2 Signal Definitions of J1 (25-Pin Male DSUB)
Table 3 lists the various signals connected to J1 on the BUF16821EVM-USB test board.
Table 3. Signal Definition of J1 (25-Pin Male DSUB) on BUF16821EVM-USB
Board
Pin on J1 Signal BUF16821 Pin
1 N/C No connection
2 N/C No connection
3 N/C No connection
4 N/C No connection
5 N/C No connection
6 N/C No connection
7 N/C No connection
8 N/C No connection
9 I2C_SCK No connection
10 I2C_SDA2 No connection
11 N/C No connection
12 I2C_SCK_ISO I2C clock signal (SCL) channel 1; can be
disconnected using a switch
13 I2C_SDA_ISO I2C data signal (SDA) channel 1; can be
disconnected using a switch
14 N/C No connection
15 N/C No connection
16 N/C No connection
17 VDUT
Switched 3V/5V power. Note that when
power is switched off, digital I/O is also
switched off.
18 VCC No connection
19 N/C No connection
20 N/C No connection
21 GND Common ground connection
22 SPI_SCK No connection
23 SPI_CS1 No connection
24 SPI_DOUT1 No connection
25 SPI_DIN1 No connection

Adjustable
Regulator
TUSB3210
8052 Cm
with USB Interface
and UART
3.3V
Regulator
8K byte
EEPROM
VCC
(2.7V to 5.5V)
V Cm
S
3.3V
VUSB
5V
VDUT
(2.7V to 5.5V)
Reset Button and
Power-On Reset
Buffers and
Latches
Calibration
EEPROM
USB DIG Platform
Power
Switching
Switched
Power
External
Power
(6V dc)
USB Bus
from
Computer
I C/SPI
2
Control and
Measure Bits
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2.2.1 Theory of Operation for USB_DIG_Platform
Figure 4 shows the block diagram for the USB_DIG_Platform. This platform is a general-purpose data
acquisition system that is used on several different Texas Instruments evaluation modules. The details of
its operation are included in a separate document, SBOU058 (available for download at www.ti.com). The
block diagram shown in Figure 4 gives a brief overview of the platform. The primary control device on the
USB_DIG_Platform is the TUSB3210. The barrel connector cable assembly included in the EVM kit can
be used to connect an external power supply to the USB DIG through J5.
Figure 4. USB_DIG_Platform Block Diagram
3 BUF16821EVM-USB Software
The BUF16821EVM-USB hardware overview involves connecting the two PCBs of the EVM together,
applying power, connecting the USB cable, and setting the jumpers. This section presents the details of
this procedure.
3.1 Electrostatic Discharge Warning
CAUTION
Many of the components on the BUF16821EVM-USB are susceptible to
damage by electrostatic discharge (ESD). Customers are advised to observe
proper ESD handling precautions when unpacking and handling the EVM,
including the use of a grounded wrist strap at an approved ESD workstation.

DC Power for
USB Dig Platform
9V
GND
USB Cable
Supply
Max = 20V
Required External
Connections
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3.2 Typical Hardware Connections
To set up the BUF16821EVM-USB hardware, connect the two PCBs of the EVM together (that is, the
BUF16821 Test Board and USB_DIG_Platform board) via a 25-pin DSUB connector, and apply a power
source. The external connections may be the real-world system that the BUF16821 will be incorporated
into. Figure 5 illustrates the typical hardware connections.
Figure 5. Typical Hardware Connections for BUF16821EVM-USB

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3.3 Connecting the Hardware
To connect the two PCBs of the BUF16821EVM-USB together, gently push on both sides of the DSUB
connectors (as shown in Figure 6). Note that the USB_DIG_Platform board has two DSUB connectors;
either may be used. Make sure that the two connectors are completely pushed together; loose
connections may cause intermittent operation.
3.4 Connecting Power
After the two parts of the BUF16821EVM-USB are conjoined, connect the power to the
USB_DIG_Platform board, as Figure 6 shows. Always connect power before connecting the USB cable. If
you connect the USB cable before connecting the power, the computer will attempt to communicate with
an unpowered device that will not be able to respond.
NOTE: It is always necessary to connect the power to the USB_DIG_Platform board before
connecting the USB cable.
In addition, the BUF16821EVM-USB also requires an external power source. This source is not included
with the kit. Its voltage may differ depending on your specific testing needs. The source will be used to
provide dc supply voltage to terminal T1 on the BUF16821EVM-USB.
Figure 6. Connecting External Power to the EVM

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3.5 Connecting the USB Cable to the USB_DIG_Platform
Once power is connected, the USB cable must be connected to the USB_DIG_Platform, as shown in
Figure 7. Note that the BUF16821EVM-USB test board and the USB_DIG_Platform board must each be
powered on before connecting the USB cable. Typically, the computer will respond with a Found New
Hardware, USB Device pop-up dialog. The pop-up window typically changes to Found New Hardware,
USB Human Interface Device. This pop-up indicates that the device is ready to be used. The
USB_DIG_Platform uses the human interface device drivers that are part of the Microsoft®Windows®
operating system.
Figure 7. Connecting the USB Cable to the USB_DIG_Platform
In some cases, the Windows Add Hardware Wizard may pop up. If this prompt appears, allow the system
device manager to install the human interface drivers by clicking Yes when requested to install drivers.
Windows will confirm installation of the drivers with the message shown in Figure 8.
Figure 8. Confirmation of USB_DIG_Platform Driver Installation

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3.6 BUF16821EVM-USB Default Jumper Settings
Figure 9 shows the default jumper configuration for the BUF16821EVM-USB. In general, the jumper
settings of the USB_DIG_Platform will not need to be changed. You may want to change some of the
jumpers on the BUF16821EVM-USB board to match your specific configuration. For example, you may
wish to set a specific I2C address.
Figure 9. BUF16821EVM-USB Default Jumper Settings
Jumpers 1 through 4 on the BUF16821EVM-USB are all typically set to the same position. When set to
the INT position, the signals from the digital supply, bank select, and the digital communication lines are
generated and controlled from the USB_DIG_Platform or by the onboard bank select switch. When these
jumpers are set to the EXT position, the previously-described signals connect to the terminal strips T2, T3,
and T4. Jumper 5 controls the I2C address pin for the BUF16821. This jumper can set the address for A0
to either high or low.

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Table 4 summarizes the function of the BUF16821EVM-USB test board jumpers. For most applications,
Jumpers 1 through 5 are all set to the default positions.
Table 4. BUF16821EVM-USB Test Board Jumper Functions
Jumper Default Purpose
JMP1
This jumper selects whether the VSD pin on the
BUF16821 is connected to the VDUT signal
generated from the USB_DIG_Platform or whether
the digital supply pin is connected to terminal T2,
allowing for an external supply to power the digital
circuitry. The default INT position connects the VSD
pin to the VDUT control signal.
JMP2
This jumper selects whether the SDA pin on the
BUF16821 is connected to the I2C_SDA_ISO signal
generated from the USB_DIG_Platform or whether
the SDA pin is connected to terminal T4, allowing
for an external source to control the I2C data line.
The default INT position connects the SDA pin to
the I2C_SDA_ISO control signal.
JMP3
This jumper selects whether the SCL pin on the
BUF16821 is connected to the I2C_SCK_ISO signal
generated from the USB_DIG_Platform or whether
the SCL pin is connected to terminal T4, allowing
for an external source to control the I2C clock line.
The default INT position connects the SCL pin to
the I2C_SCK_ISO control signal.
JMP4
This jumper selects whether the BKSEL pin on the
BUF16821 is controlled by the manual switch
located on the BUF16821EVM-USB or whether the
BKSEL can be controlled by an external source
connected to terminal T3. The default INT position
allows the BKSEL pin to be controlled by the
manual switch.
JMP5 This jumper selects the I2C A0 address. Two separate I2C addresses can be selected depending
upon whether JMP1 is set to high or low.
Table 5 summarizes the function of the USB_DIG_Platform jumpers. For most applications, the default
jumper position should be used. A separate document (SBOU058) gives details regarding the operation
and design of the USB_DIG_Platform.
Table 5. USB_DIG_Platform Jumper Functions
Jumper Default Purpose
JUMP1 EXT This jumper selects external power or bus power.
External power is applied on J5 or T3 (9V dc). Bus
power is 5V from the USB bus. External power is
typically used because the USB Bus power is noisy.
JUMP2 EXT Same as JUMP1.
JUMP3 EE ON This jumper determines where the TUSB3210 will
load the USB_DIG_Platform firmware upon power-
up or reset. The EE Off position is used for
development for development or firmware update.
JUMP4, JUMP5 L, L This jumper sets the address for the USB board. The only reason to change from the default setting
is if multiple boards are being used.
JUMP9 5V This jumper selects the voltage of the device under
test supply (VDUT = 5V or 3V). This jumper is
typically the only jumper that is changed for most
applications.
JUMP10 WP ON This write protects the firmware EEPROM.
JUMP11 WP ON This write protects the calibration EEPROM.

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Table 5. USB_DIG_Platform Jumper Functions (continued)
Jumper Default Purpose
(1) CAUTION: Adjusting outside of this range will damage the EVM.
JUMP13 REG Uses the regulator output to generate the VDUT supply. The USB bus can be used as the VDUT
supply.
JUMP14 9V Uses the external power (9V as opposed to the
bus).
JUMP17 BUS While in the BUS position VDUT operation is normal.
While in the VRAW position the VDUT supply is
connected to an external source. This configuration
allows for any value of VDUT between 3V and 5V.(1)
JUMP18 VDUT Connects the pull-up on GPIO to the VDUT supply or
the VCC supply.
3.7 BUF16821EVM-USB Features
This section describes some of the hardware features present on the BUF16821EVM-USB test board.
3.7.1 BKSEL: OTP Bank Selection Switch
The BKSEL switch located on the BUF16821EVM-USB Test Board selects the memory bank to be used
when operating the EVM. Bank 0 selects the gamma curve that is stored in Bank_0 of the BUF16821.
Bank 1 selects the gamma curve that is stored in Bank_1 of the BUF16821. This switch also determines
the OTP bank that is written to by the BUF16821EVM-USB software. Note that this switch is not effective
if JMP4 is set to EXT.
3.7.2 JMP1: I2C SCK Control Setting
Jumper JMP1 selects where the BUF16821 digital supply pin is connected. If JMP1 is set in the INT
position, the VSD pin is connected to the switchable VDUT signal generated from the USB DIG Platform.
This voltage can be set to either 3.3V or 5V depending on how JUMP9 on the USB DIG Platform is set.
While JMP1 is set to the INT position, the VSD Power button on the BUF16821 software is able to control
whether the VDUT supply voltage is turned on or off.
When JMP1 is set in the EXT position, an external supply connected to terminal T2 can be used to
provide the digital supply voltage for the BUF16821.
3.7.3 JMP2: VSD Control Setting
Jumper JMP2 selects where the BUF16821 I2C SDA pin is connected. If JMP2 is set in the INT position,
the I2C data signal is generated from the I2C_SDA_ISO signal from the USB DIG Platform.
When JMP2 is set in the EXT position, an external source connected to SDA pin of terminal T4 can be
used to provide the I2C SDA signal for the BUF16821.
3.7.4 JMP3: BKSEL Control Setting
Jumper JMP3 selects where the BUF16821 I2C SCL pin is connected. If JMP3 is set in the INT position,
the I2C clock signal is generated from the I2C_SCK_ISO signal from the USB DIG Platform.
When JMP3 is set in the EXT position, an external source connected to SCL pin of terminal T4 can be
used to provide the I2C SCK signal for the BUF16821.
3.7.5 JMP4: I2C SDA Control Setting
Jumper JMP4 determines how the OTP memory bank selection is controlled. There are two settings JMP4
can be set to. Position INT specifies that control of the BKSEL pin is handled on the BUF16821 Test
Board by the BKSEL switch. Position EXT for JMP4 allows for an external control signal connected to
terminal T3 to determine the selection of which OTP bank to be used.

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3.7.6 JMP5: I2C Address Hardware Setting
Jumper JMP5 is used to set the hardware setting for the A0 I2C address pin on the BUF16821. Using
JMP5, the A0 address can be set to either logic “1” or logic “0” to allow for two unique I2C addresses. See
the section 5.2.1 on how to configure the BUF16821EVM software to match the JMP1 hardware setting.
3.7.7 BUF16821 Device Placement
The BUF16821EVM-USB allows the user two separate locations on the board where the BUF16821 test
device can be installed.
The U2 location allows for a BUF16821 device that is soldered down on a DIP adaptor board to be
installed on the BUF16821EVM. The output capability of the BUF16821 that is soldered on this adaptor
board can be fully evaluated. The power pad of this soldered BUF16821 is connected correctly allowing
the device to dissipate the necessary power while being evaluated.
The U1 location on the BUF16821EVM is a 28-pin test socket that allows the user to evaluate and
program many devices very quickly. One drawback to this socket is that there is no connection to the
PowerPAD™ of the BUF16821. Because of this drawback, while mounted in this socket, the BUF16821
cannot be operated at its full output capability as a result of thermal dissipation limitations.
CAUTION
Only one location should be populated at a time. The use of both locations
simultaneously will damage one or both of the devices being tested.
3.7.8 Terminal Strip TPG1
Terminal strip TPG1 provides the individual output signals on a single row of headers as well as a row of
vias. This footprint provides the user with multiple options regarding how to interface the output signals of
the BUF16821 with the available display panel. Users can develop a custom cable to connect the headers
to their respective panels directly, or to solder directly to the individual vias.
4 BUF16821EVM-USB Software
4.1 Hardware Requirements
The BUF16821EVM-USB software has been tested on Microsoft®Windows®XP, Vista, and Windows 7
operating systems (OS) with United States and European regional settings.
4.2 Software Installation
The BUF16821EVM-USB software is included on the CD that is shipped with the EVM kit. It is also
available through the BUF16821EVM-USB product folder on the TI website. To install the software to a
computer, insert the disc into an available CD-ROM drive. Navigate to the drive contents and open the
BUF16821EVM-USB software folder. Locate the compressed file (BUF16821EVM-USB.zip) and open it
using WinZIP®or a similar file compression program; extract the BUF16821EVM-USB files into a specific
BUF16821EVM-USB folder (for example, C:\BUF16821EVM-USB) on your hard drive.

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Once the files are extracted, navigate to the BUF16821EVM-USB folder you created on the hard drive.
Locate the setup.exe file and execute it to start the installation. The BUF16821 software installer file then
begins the installation process as shown in Figure 10.
Figure 10. BUF16821EVM-USB Software Installation

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After the installation process initializes, the user is given the choice of selecting the directory in which to
install the program; the default location is C:\Program Files\BUF16821\ and C:\Program Files\National
Instruments\. Following this option, two license agreements are presented that must be accepted, as
shown in Figure 11. After accepting the Texas Instruments and National Instruments license agreements,
the progress bar opens and shows the installation of the software, as Figure 12 illustrates. Once the
installation process is completed, click Finish.
Figure 11. BUF16821EVM-USB License Agreements
Figure 12. BUF16821EVM-USB Software Installation Progress

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4.3 Software Description and Set-Up
The BUF16821EVM-USB software allows the user to read and write to all registers in the BUF16821
gamma correction buffer. Furthermore, it allows programming of the OTP register on the BUF16821. The
software also permits the user to select either I2C address. Press the About button, as shown in
Figure 13, to verify that you have the latest version of the software.
Figure 13. BUF16821EVM-USB Software About Button
5 BUF16821EVM-USB Software Overview
This section discusses how to use the BUF16821EVM-USB software.
5.1 Starting the BUF16821EVM-USB Software
The BUF16821 software can be operated through the Windows Start menu. From Start, select All
Programs; then select the BUF16821EVM-USB program.
Figure 14 shows an error that pops up if the computer cannot communicate with the EVM. If you receive
this error, first check to see that the USB cable is properly connected on both ends. This error can also
occur if you connect the USB cable before the USB_DIG_Platform power source. Another possible source
for this error is a problem with your PC USB Human Interface Device driver. Make sure that the device is
recognized when the USB cable is plugged in; recognition is indicated by a Windows-generated
confirmation sound.
Figure 14. BUF16821EVM-USB Software: Communication Error with the USB_DIG_Platform

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5.2 Using the BUF16821Software
5.2.1 I2C Address Selection
As mentioned previously in the BUF16821EVM-USB Features section (see Section 3.7), jumper JMP5 is
used to set the I2C address pin of the BUF16821. Figure 15 shows how both the hardware and software
must be set to allow for communication between the BUF16821EVM-USB and the software. Without
jumper JMP5 and the software address button configured correctly, the software will not be able to
communicate with the BUF16821 device.
Figure 15. JMP5 Setting For Logic ‘1’
When JMP5 and the software are set as Figure 16 shows, the second I2C address can be configured.
Figure 16. JMP5 Setting for Logic ‘0’

V =
CHANNEL
V Code
1024
SUP ?
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5.2.2 Measuring the Power Supply
You must measure the power supply (VS) with respect to the GND on the BUF16821EVM-USB test board
and enter it in the VSUP field located in the top section of the software interface, as shown in Figure 17.
Figure 17. Measuring and Entering Power-Supply Voltage
The voltages calculated for each channel are based on the value entered as VSUP, as shown in Equation 1.
Note that Code is the value found in the channel registry converted to decimal format.
(1)
5.2.3 Read DAC Button
By pressing the Read DAC button in the BUF16821EVM-USB software, all of the BUF16821 DAC/VCOM
registers are read to obtain the respective current register contents. Once the read procedure is complete,
all of the corresponding text boxes are updated to show the current values present in the DAC/VCOM
registers.

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BUF16821EVM-USB Evaluation Board and Software Tutorial
5.2.4 Write DAC Button
The method used to write the values in the DAC/VCOM registers is based on whether or not the Auto Write
feature is enabled. The BUF16821 has two methods of writing information into the DAC/VCOM registers.
The first method allows for the output voltage to change immediately after the writing to the DAC register.
In the BUF16821EVM-USB software, this mode is configured by enabling the Auto Write feature found in
the Buffer 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/VCOM 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/VCOM register; thus, no change occurs.
Figure 18 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 18. Auto Write Feature Enabled
5.2.5 Reset Button
Pressing the Reset button in the BUF16821EVM-USB software performs two functions. The first function
is to call a General-Call Reset for the BUF16821. The status of the DAC/VCOM registers after this General-
Call Reset has been called depends upon whether the OTP has been programmed or not. If the OTP has
been programmed, the channel registers are loaded with the most recent values programmed into the
OTP memory. If the OTP memory has not been programmed, the channel registers 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.