BUF22821 Datasheet, PDF (11/25 Pages) Texas Instruments – Programmable Gamma-Voltage Generator and VCOM Calibrator with Integrated Two-Bank Memory

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The I²C master also has the ability to update
(acquire) the DAC registers with the last
programmed nonvolatile memory values using
software control. The bank to be acquired depends
on the state of BKSEL.
General Acquire Command
A general acquire command is used to update all
registers and DAC/V_COM outputs to the last
programmed values stored in nonvolatile memory. A
single-channel acquire command updates only the
register and DAC/V_COM output of the DAC/V_COM
corresponding to the DAC/V_COM address used in the
single-channel acquire command.
The sequence to initiate a general channel acquire is
as follows:
1. Be sure BKSEL is in its desired state and has
been stable for at least 1ms.
2. Send a START condition on the bus.
3. Send the appropriate device address (based
on A0) and the read/write bit = LOW. The
BUF22821 acknowledges this byte.
4. Send a DAC/V_COM pointer address byte. Set
bit D7 = 1 and D6 = 0. Bits D5–D0 are any
valid DAC/V_COM address. Only addresses
000000 to 010111 are valid and are
acknowledged. See Table 5 for valid
DAC/V_COM addresses.
5. Send a STOP condition on the bus.
Approximately 750µs (±80µs) after issuing this
command, all DAC/V_COM registers and DAC/V_COM
output voltages change to the respective, appropriate
nonvolatile memory values.
Single-Channel Acquire Command
The sequence to initiate a single-channel acquire is
as follows:
1. Be sure BKSEL is in its desired state and has
been stable for at least 1ms.
2. Send a START condition on the bus.
3. Send the device address (based on A0) and
read/write bit = LOW. The BUF22821
acknowledges this byte.
4. Send a DAC/V_COM pointer address byte using
the DAC/V_COM address corresponding to the
output and register to update with the OTP
memory value. Set bit D7 = 0 and D6 = 1. Bits
D5–D0 are the DAC/V_COM address. Only
addresses 000000 to 010111 are valid and
are acknowledged. See Table 5 for valid
DAC/V_COM addresses.
5. Send a STOP condition on the bus.
BUF22821
SBOS399 – JUNE 2007
Approximately 36µs (±4µs) after issuing this
command, the specified DAC/V_COM register and
DAC/V_COM output voltage change to the appropriate
OTP memory value.
MaxBank
The BUF22821 can provide the user with the number
of times the nonvolatile memory of a particular
DAC/V_COM channel nonvolatile memory has been
written to for the current memory bank. This
information is provided by reading the register at
pointer address 111111.
There are two ways to update the MaxBank register:
1. After initiating a single-acquire comand, the
BUF22821 updates the MaxBank register with
a code corresponding to how many times that
particular channel memory has been written
to.
2. Following a general-acquire command, the
BUF22821 updates the MaxBank register with
a code corresponding to the maximum
number of times the most used channel
(OUT1–22 and V_COMs) has been written to.
MaxBank is a read-only register and is only updated
by performing a general- or single-channel acquire.
Table 3 shows the relationship between the number
of times the nonvolatile memory has been
programmed and the corresponding state of the
MaxBank Register.
Table 3. MaxBank Details
TIMES WRITTEN TO
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
RETURNS CODE
0000
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100
1101
1110
1111
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