BUF16821 datasheet(12/29 Pages) EPCOS

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READ/WRITE OPERATIONS

Read/Write: DAC/VCOM Register (volatile memory)

Writing: DAC/VCOM Register (Volatile Memory)

Parity Error Correction

DIE_ID AND DIE_REV REGISTERS

BUF16821

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

Table 3 shows the relationship between the number

times

the

nonvolatile

memory

has

been

Read and write operations can be done for a single

programmed and the corresponding state of the

DAC/VCOM or for multiple DACs/VCOMs. Writing to a

MaxBank Register.

DAC/VCOM register differs from writing to the

nonvolatile memory. Bits D15–D14 of the most

Table 3. MaxBank Details

significant byte of data determines if data are written

NUMBER OF TIMES WRITTEN TO

RETURNS CODE

to the DAC/VCOM register or the nonvolatile memory.

0000

0001

The BUF16821 is able to read from a single

0010

DAC/VCOM, or multiple DACs/VCOMs, or write to the

0011

single

DAC/VCOM,

multiple

0100

DACs/VCOMs in a single communication transaction.

0101

DAC pointer addresses begin with 000000 (which

corresponds

OUT1)

through

001111

(which

0110

corresponds to OUT16). Addresses 010010 and

0111

010011 are VCOM1 and VCOM2, respectively.

1000

1001

Write commands are performed by setting the

1010

read/write bit LOW. Setting the read/write bit HIGH

performs a read transaction.

1011

1100

1101

1110

To write to a single DAC/VCOM register:

1111

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 a DAC/VCOM pointer address byte. Set bit

The

BUF16821

provides

single-bit

parity

error

D7 = 0 and D6 = 0. Bits D5–D0 are the

correction for data stored in the nonvolatile memory

DAC/VCOM address. Although the BUF16821

to provide increased reliability of the nonvolatile

acknowledges 000000 through 010111, it stores

memory. If a single bit of nonvolatile memory for a

and returns data only from these addresses:

channel fails, the BUF16821 corrects for it and

updates the appropriate DAC with the intended value

–

000000 through 001111

when its memory is acquired.

–

010010 through 010011

It returns 0000 for reads from 010000 through

If more than one bit of nonvolatile memory for a

010001,

and

010100

through

010111.

See

channel fails, the BUF16821 does not correct for it,

Table 4 for valid DAC/VCOM addresses.

and updates the appropriate DAC/VCOM with the

default value of 1000000000.

4. Send two bytes of data for the specified register.

Begin by sending the most significant byte first

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

used, and bits D15–D14 must not be 01),

The user can verify the presence of the BUF16821 in

followed

the

least

significant

byte

(bits

the system by reading from address 111101. The

D7–D0). The register is updated after receiving

BUF16821 returns 0101100100100111 when read at

the second byte.

this address.

5. Send a STOP or START condition on the bus.

The user can also determine the die revision of the

BUF16821

reading

from

111100.

BUF16821 returns 0000000000000000 when a RevA

die is present. RevB would be designated by

0000000000000001 and so on.

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