BUF16821 Datasheet, PDF (14/29 Pages) EPCOS – Programmable Gamma-Voltage Generator and VCOM Calibrator with Integrated Two-Bank Memory

BUF16821
SBOS428 – JULY 2008 ...................................................................................................................................................................................................... www.ti.com
Communication may be terminated by sending a
premature STOP or START condition on the bus, or
by not acknowledging.
To read multiple registers:
1. Send a START condition on the bus.
2. Send the device address and read/write bit =
LOW. The BUF16821 acknowledges this byte.
3. Send either the OUT1 pointer address byte to
start at the first DAC, or send the pointer address
byte for whichever register is the first in the
sequence of DACs/V_COMs to be read. The
BUF16821 begins with this DAC/V_COM and steps
through subsequent DACs/V_COMs in sequential
order.
4. Send a START or STOP/START condition on the
bus.
5. Send the correct device address and read/write
bit = HIGH. The BUF16821 acknowledges this
byte.
6. Receive two bytes of data. They are for the
specified DAC/V_COM. The first received byte is the
most significant byte (bits D15–D8; only bits D9
and D8 have meaning), next is the least
significant byte (bits D7–D0).
7. Acknowledge after receiving each byte of data.
8. When all desired DACs have been read, send a
STOP or START condition on the bus.
Communication may be terminated by sending a
premature STOP or START condition on the bus, or
by not sending the acknowledge bit. The reading of
registers DieID, DieRev, and MaxBank is not
supported in this mode of operation (these values
must be read using the single register read method).
Write: Nonvolatile Memory for the DAC Register
The BUF16821 is able to write to the nonvolatile
memory of a single DAC/V_COM in a single
communication transaction. In contrast to the
BUF20820, writing to multiple nonvolatile memory
words in a single transaction is not supported. Valid
DAC/V_COM pointer addresses begin with 000000
(which corresponds to OUT1) through 001111 (which
corresponds to OUT16). Addresses 010010 and
010011 are V_COM1 and V_COM2, respectively.
When programming the nonvolatile memory, the
analog supply voltage must be between 9V and 20V.
Write commands are performed by setting the
read/write bit LOW.
To write to a single nonvolatile register:
1. Send a START condition on the bus.
2. Send the device address and read/write bit =
LOW. The BUF16821 acknowledges this byte.
Although the BUF16821 acknowledges 000000
through 010111, it stores and returns data only
from these addresses:
– 000000 through 001111
– 010010 and 010011
It returns 0000 for reads from 010000 through
010001, and 010100 through 010111. See
Table 4 for DAC/V_COM addresses.
3. Send a DAC/V_COM pointer address byte. Set bit
D7 = 0 and D6 = 0. Bits D5–D0 are the
DAC/V_COM address.
4. Send two bytes of data for the nonvolatile register
of the specified DAC/V_COM. Begin by sending the
most significant byte first (bits D15–D8, of which
only bits D9 and D8 are data bits, and bits
D15–D14 must be 01), followed by the least
significant byte (bits D7–D0). The register is
updated after receiving the second byte.
5. Send a STOP condition on the bus.
The BUF16821 acknowledges each data byte. If the
master terminates communication early by sending a
STOP or START condition on the bus, the specified
nonvolatile register is not updated. Writing a
nonvolatile register also updates the DAC/V_COM
register and output voltage.
The DAC/V_COM register and DAC/V_COM output voltage
are updated immediately, while the programming of
the nonvolatile memory takes up to 250µs. Once a
nonvolatile register write command has been issued,
no communication with the BUF16821 should take
place for at least 250µs. Writing or reading over the
serial interface while the nonvolatile memory is being
written jeopardizes the integrity of the data being
stored.
Read: Nonvolatile Memory for the DAC Register
To read the data present in nonvolatile register for a
particular DAC/V_COM channel, the master must first
issue a general acquire command, or a single acquire
command with the appropriate DAC/V_COM channel
chosen. This action updates both the DAC/V_COM
register(s) and DAC/V_COM output voltage(s). The
master may then read from the appropriate
DAC/V_COM register as described earlier.
14
Submit Documentation Feedback
Product Folder Link(s): BUF16821
Copyright © 2008, Texas Instruments Incorporated