BUF16821 Datasheet, PDF (12/29 Pages) EPCOS – Programmable Gamma-Voltage Generator and VCOM Calibrator with Integrated Two-Bank Memory

BUF16821
SBOS428 – JULY 2008 ...................................................................................................................................................................................................... www.ti.com
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
NUMBER OF 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
Parity Error Correction
The BUF16821 provides single-bit parity error
correction for data stored in the nonvolatile memory
to provide increased reliability of the nonvolatile
memory. If a single bit of nonvolatile memory for a
channel fails, the BUF16821 corrects for it and
updates the appropriate DAC with the intended value
when its memory is acquired.
If more than one bit of nonvolatile memory for a
channel fails, the BUF16821 does not correct for it,
and updates the appropriate DAC/V_COM with the
default value of 1000000000.
DIE_ID AND DIE_REV REGISTERS
The user can verify the presence of the BUF16821 in
the system by reading from address 111101. The
BUF16821 returns 0101100100100111 when read at
this address.
The user can also determine the die revision of the
BUF16821 by reading from register 111100.
BUF16821 returns 0000000000000000 when a RevA
die is present. RevB would be designated by
0000000000000001 and so on.
READ/WRITE OPERATIONS
Read and write operations can be done for a single
DAC/V_COM or for multiple DACs/V_COMs. Writing to a
DAC/V_COM register differs from writing to the
nonvolatile memory. Bits D15–D14 of the most
significant byte of data determines if data are written
to the DAC/V_COM register or the nonvolatile memory.
Read/Write: DAC/V_COM Register (volatile memory)
The BUF16821 is able to read from a single
DAC/V_COM, or multiple DACs/V_COMs, or write to the
register of a single DAC/V_COM, or multiple
DACs/V_COMs in a single communication transaction.
DAC pointer addresses begin with 000000 (which
corresponds to OUT1) through 001111 (which
corresponds to OUT16). Addresses 010010 and
010011 are V_COM1 and V_COM2, respectively.
Write commands are performed by setting the
read/write bit LOW. Setting the read/write bit HIGH
performs a read transaction.
Writing: DAC/V_COM Register (Volatile Memory)
To write to a single DAC/V_COM register:
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/V_COM pointer address byte. Set bit
D7 = 0 and D6 = 0. Bits D5–D0 are the
DAC/V_COM address. Although the BUF16821
acknowledges 000000 through 010111, it stores
and returns data only from these addresses:
– 000000 through 001111
– 010010 through 010011
It returns 0000 for reads from 010000 through
010001, and 010100 through 010111. See
Table 4 for valid DAC/V_COM addresses.
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),
followed by the least significant byte (bits
D7–D0). The register is updated after receiving
the second byte.
5. Send a STOP or START condition on the bus.
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