BUF16821 datasheet(11/29 Pages) EPCOS

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Single-Channel Acquire Command

General Acquire Command

MaxBank

BUF16821

www.ti.com ...................................................................................................................................................................................................... SBOS428 – JULY 2008

When the BKSEL pin changes state, the BUF16821

acquires the last programmed DAC/VCOM values from

These are the steps to initiate a single-channel

the nonvolatile memory associated with this newly

acquire:

chosen bank. At power-up, the state of the BKSEL

1. Be sure BKSEL is in its desired state and has

pin determines which memory bank is selected.

been stable for at least 1ms.

The I2C master also has the ability to update

2. Send a START condition on the bus.

(acquire) the DAC registers with the last programmed

3. Send the device address (based on A0) and

nonvolatile memory values using software control.

read/write

bit

LOW.

The

BUF16821

The bank to be acquired depends on the state of

acknowledges this byte.

BKSEL.

4. Send a DAC/VCOM pointer address byte using the

DAC/VCOM address corresponding to the output

and register to update with the OTP memory

A general acquire command is used to update all

value. Set bit D7 = 0 and D6 = 1. Bits D5–D0 are

registers

and

DAC/VCOM

outputs

the

last

the DAC/VCOM address. Although the BUF16821

programmed values stored in nonvolatile memory. A

acknowledges 000000 through 010111, it stores

single-channel acquire command updates only the

and returns data only from these addresses:

–

000000 through 001111

corresponding to the DAC/VCOM address used in the

–

010010 and 010011

single-channel acquire command.

It returns 0000 reads from 010000 and 010001,

These are the steps of the sequence to initiate a

and 010100 through 010111. See Table 4 for

general channel acquire:

valid DAC/VCOM addresses.

1. Be sure BKSEL is in its desired state and has

5. Send a STOP condition on the bus.

been stable for at least 1ms.

Approximately

µs (±4µs) after issuing this

2. Send a START condition on the bus.

command, the specified DAC/VCOM register and

3. Send the appropriate device address (based on

DAC/VCOM output voltage change to the appropriate

A0) and the read/write bit = LOW. The BUF16821

OTP memory value.

acknowledges this byte.

4. Send a DAC/VCOM pointer address byte. Set bit

D7 = 1 and D6 = 0. Bits D5–D0 are any valid

The BUF16821 can provide the user with the number

DAC/VCOM address. Although the BUF16821

of times the nonvolatile memory of a particular

acknowledges 000000 through 010111, it stores

DAC/VCOM channel nonvolatile memory has been

and returns data only from these addresses:

written

for

the

current

memory

bank.

This

–

000000 through 001111

information is provided by reading the register at

–

010010 and 010011

pointer address 111111.

It returns 0000 for reads from 010000 and

There are two ways to update the MaxBank register:

010001,

and

010100

through

010111.

See

Table 4 for valid DAC/VCOM addresses.

1. After initiating a single acquire comand, the

BUF16821 updates the MaxBank register with a

5. Send a STOP condition on the bus.

code corresponding to how many times that

Approximately

750

µs (±80µs) after issuing this

particular channel memory has been written to.

command, all DAC/VCOM registers and DAC/VCOM

2. Following

general

acquire

command,

the

output voltages change to the respective, appropriate

BUF16821 updates the MaxBank register with a

nonvolatile memory values.

code corresponding to the maximum number of

times the most used channel (OUT1–16 and

xxx

VCOMs) has been written to.

xxx

MaxBank is a read-only register and is only updated

by performing a general- or single-channel acquire.

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