BUF12840 datasheet(13/31 Pages) TI1

13 / 31 page

BUF12840

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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

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

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

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

nonvolatile memory values using software control.

The bank to be acquired depends on the state of

BKSEL.

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