BUF22821 Datasheet, PDF (13/25 Pages) Texas Instruments – Programmable Gamma-Voltage Generator and VCOM Calibrator with Integrated Two-Bank Memory

www.ti.com
Reading: DAC/V_COM/OTHER Register (volatile
memory)
Reading a register returns the data stored in that
DAC/V_COM/OTHER register.
To read a single DAC/V_COM/OTHER register:
1. Send a START condition on the bus.
2. Send the device address and read/write bit =
LOW. The BUF22821 acknowledges this byte.
3. Send the DAC/V_COM/OTHER pointer address
byte. Set bit D7 = 0 and D6 = 0; bits D5–D0
are the DAC/V_COM/OTHER address. Only
addresses 000000–010111, 111100, 111101,
and 111111 are valid and are acknowledged.
4. Send a START or STOP/START condition.
5. Send the correct device address and
read/write bit = HIGH. The BUF22821
acknowledges this byte.
6. Receive two bytes of data. They are for the
specified register. The most significant byte
(bits D15–D8) is received first; next is the
least significant byte (bits D7–D0). In the case
of DAC/V_COM channels, bits D15–D10 have no
meaning.
7. Acknowledge after receiving the first byte.
8. Send a STOP or START condition on the bus
or do not acknowledge the second byte to end
the read transaction.
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 BUF22821 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 BUF22821 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 BUF22821
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.
BUF22821
SBOS399 – JUNE 2007
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 (they must be
read using the single register read method).
Write: Nonvolatile Memory for the DAC Register
The BUF22821 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 010111 (which
corresponds to OUT22).
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 BUF22821 acknowledges this byte.
Only addresses 000000 to 010111 are valid
and are acknowledged. See Table 5 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 BUF22821 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
Submit Documentation Feedback
13