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Reading:

DAC/VCOM/OTHER Register (volatile

Write: Nonvolatile Memory for the DAC Register

BUF22821

SBOS399 – JUNE 2007

8. When all desired DACs have been read, send

memory)

a STOP or START condition on the bus.

Reading a register returns the data stored in that

Communication may be terminated by sending a

DAC/VCOM/OTHER register.

premature STOP or START condition on the bus, or

by not sending the acknowledge bit. The reading of

To read a single DAC/VCOM/OTHER register:

registers

DieID,

DieRev,

and

MaxBank

not

1. Send a START condition on the bus.

supported in this mode of operation (they must be

2. Send the device address and read/write bit =

read using the single register read method).

LOW. The BUF22821 acknowledges this byte.

3. Send the DAC/VCOM/OTHER pointer address

byte. Set bit D7 = 0 and D6 = 0; bits D5–D0

The BUF22821 is able to write to the nonvolatile

are the DAC/VCOM/OTHER address. Only

memory

single

DAC/VCOM in a single

addresses 000000–010111, 111100, 111101,

communication

transaction.

contrast

the

and 111111 are valid and are acknowledged.

BUF20820, writing to multiple nonvolatile memory

4. Send a START or STOP/START condition.

words in a single transaction is not supported. Valid

DAC/VCOM pointer addresses begin with 000000

5. Send

the

correct

device

address

and

(which corresponds to OUT1) through 010111 (which

read/write

bit

HIGH.

The

BUF22821

corresponds to OUT22).

acknowledges this byte.

6. Receive two bytes of data. They are for the

When programming the nonvolatile memory, the

specified register. The most significant byte

analog supply voltage must be between 9V and 20V.

(bits D15–D8) is received first; next is the

Write commands are performed by setting the

least significant byte (bits D7–D0). In the case

read/write bit LOW.

of DAC/V

COM channels, bits D15–D10 have no

meaning.

To write to a single nonvolatile register:

7. Acknowledge after receiving the first byte.

1. Send a START condition on the bus.

8. Send a STOP or START condition on the bus

2. Send the device address and read/write bit =

or do not acknowledge the second byte to end

LOW. The BUF22821 acknowledges this byte.

the read transaction.

Only addresses 000000 to 010111 are valid

and are acknowledged. See Table 5 for

Communication may be terminated by sending a

DAC/VCOM addresses.

premature STOP or START condition on the bus, or

3. Send a DAC/VCOM pointer address byte. Set

by not acknowledging.

bit D7 = 0 and D6 = 0. Bits D5–D0 are the

To read multiple registers:

DAC/VCOM address.

1. Send a START condition on the bus.

4. Send two bytes of data for the nonvolatile

2. Send the device address and read/write bit =

LOW. The BUF22821 acknowledges this byte.

sending the most significant byte first (bits

D15–D8, of which only bits D9 and D8 are

3. Send either the OUT1 pointer address byte to

data bits, and bits D15–D14 must be 01),

start at the first DAC, or send the pointer

followed by the least significant byte (bits

address byte for whichever register is the first

D7–D0).

The

updated

after

in the sequence of DACs/VCOMs to be read.

receiving the second byte.

The BUF22821 begins with this DAC/VCOM

and steps through subsequent DACs/VCOMs in

5. Send a STOP condition on the bus.

sequential order.

The BUF22821 acknowledges each data byte. If the

4. Send a START or STOP/START condition on

master terminates communication early by sending a

the bus.

STOP or START condition on the bus, the specified

5. Send

the

correct

device

address

and

nonvolatile

not

updated.

Writing

read/write

bit

HIGH.

The

BUF22821

nonvolatile register also updates the DAC/VCOM

acknowledges this byte.

6. Receive two bytes of data. They are for the

The

DAC/VCOM register and DAC/VCOM output

specified DAC/VCOM. The first received byte is

voltage

are

updated

immediately,

while

the

the most significant byte (bits D15–D8, only

programming of the nonvolatile memory takes up to

bits D9 and D8 have meaning), next is the

250

µs. Once a nonvolatile register write command

least significant byte (bits D7–D0).

7. Acknowledge after receiving each byte of

data.

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