Datasheet

BUF12840
www.ti.com SBOS519A –OCTOBER 2010– REVISED JULY 2011
READ AGAIN Method 2: Set LD high to allow all DAC output
voltages to retain the respective values during data
When the BUF12840 is in slave mode, a read again
transfer until LD goes low, which simultaneously
(RA) command can be issued to restart an EEPROM
updates the output voltages of all 12 DACs to the
data download. The RA command follows this
new register values.
process:
Method 3 (software mode): LD is maintained high
1. Send the BUF12840 device address with write
and all 12 DACs are updated when the master writes
bit: 11101000 if A0 = 0 or 11101010 if A0 = 1; the
a '1' in bit 15 of any DAC register. The update occurs
BUF12840 acknowledges this byte.
after receiving the 16-bit data for the currently-written
2. Send register address 00011100; the BUF12840
register.
acknowledges this byte.
Use methods 2 and 3 to transfer a future data set into
3. Send two bytes of data xxxxxxxx and xxxxxxx1,
the first bank of registers in advance to prepare for a
where x is don’t care; the BUF12840
very fast update of DAC output voltages.
acknowledges both bytes.
The general-call reset (GCR) and the power-up reset
DAC OUTPUT UPDATE (Using the LD Pin)
updates the DACs regardless of the state of the latch
pin. For a list of DAC addresses; see Table 5.
Because the BUF12840 features a double-buffered
register structure, updating the DAC register is not
BKSEL PIN
the same as updating the DAC output voltage.
There are three methods for launching transferred
The BUF12840 has the ability to store two distinct
data from the storage registers into the DACs to
gamma curves in two different memory banks. One of
update the DAC output voltage. It is essential that
the two available banks is selected using the external
BKSEL be set to the desired bank because BKSEL
input pin, BKSEL. When this pin is low, BANK0 is
determines which bank is loaded.
selected; when this pin is high, BANK1 is selected.
Method 1: Set the latch pin low (LD = low) to update
The two-wire master also has the ability to update
each DAC output voltage whenever its corresponding
(acquire) the DAC registers with the last programmed
register is updated.
nonvolatile memory values using software control.
The bank to be acquired depends on the state of
BKSEL.
Copyright © 2010–2011, Texas Instruments Incorporated 13