BUF12840_15 Datasheet, PDF (13/31 Pages) Texas Instruments – Programmable Gamma-Voltage Generator

BUF12840
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READ AGAIN
When the BUF12840 is in slave mode, a read again
(RA) command can be issued to restart an EEPROM
data download. The RA command follows this
process:
1. Send the BUF12840 device address with write
bit: 11101000 if A0 = 0 or 11101010 if A0 = 1; the
BUF12840 acknowledges this byte.
2. Send register address 00011100; the BUF12840
acknowledges this byte.
3. Send two bytes of data xxxxxxxx and xxxxxxx1,
where x is don’t care; the BUF12840
acknowledges both bytes.
DAC OUTPUT UPDATE (Using the LD Pin)
Because the BUF12840 features a double-buffered
register structure, updating the DAC register is not
the same as updating the DAC output voltage.
There are three methods for launching transferred
data from the storage registers into the DACs to
update the DAC output voltage. It is essential that
BKSEL be set to the desired bank because BKSEL
determines which bank is loaded.
Method 1: Set the latch pin low (LD = low) to update
each DAC output voltage whenever its corresponding
register is updated.
SBOS519A – OCTOBER 2010 – REVISED JULY 2011
Method 2: Set LD high to allow all DAC output
voltages to retain the respective values during data
transfer until LD goes low, which simultaneously
updates the output voltages of all 12 DACs to the
new register values.
Method 3 (software mode): LD is maintained high
and all 12 DACs are updated when the master writes
a '1' in bit 15 of any DAC register. The update occurs
after receiving the 16-bit data for the currently-written
register.
Use methods 2 and 3 to transfer a future data set into
the first bank of registers in advance to prepare for a
very fast update of DAC output voltages.
The general-call reset (GCR) and the power-up reset
updates the DACs regardless of the state of the latch
pin. For a list of DAC addresses; see Table 5.
BKSEL PIN
The BUF12840 has the ability to store two distinct
gamma curves in two different memory banks. One of
the two available banks is selected using the external
input pin, BKSEL. When this pin is low, BANK0 is
selected; when this pin is high, BANK1 is selected.
The two-wire 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.
Copyright © 2010–2011, Texas Instruments Incorporated
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