ack

w

ack

ack

stop

start

msb Chip Address lsb

msb Register Add lsb

msb

DATA

lsb

ack from slave

SCL

SDA

start

w ack

id = h'xx

addr = h'02

ack

address h'02 data

ack

stop

ack from slave

ack from slave

w = write (SDA = 0) r = read (SDA = 1) ack = acknowledge (SDA pulled LOW by either master or slave) rs = repeated start xx = 60 to 67

Figure 6-4. LP3943 Register Write

However, if a READ function is to be accomplished, a WRITE function must precede the READ function, as

shown in Figure 6-5.

ack

w

ack

rs

r

ack

ack stop

start

msb Chip Address lsb

msb Register Add lsb

msb Chip Address lsb

msb

DATA

lsb

ack from slave

SCL

SDA

ack from slave

ack from slave

ack from master

data from slave

repeated start

start

w ack

addr = h'00

ack

rs

r ack

address h'00 data

ack

stop

id = h'xx

id = h'xx

w = write (SDA = “0”) r = read (SDA = “1”) ack = acknowledge (SDA pulled LOW by either master or slave) rs = repeated start xx = 60 to

67

Figure 6-5. LP3943 Register Read

6.5.4 Auto Increment

Auto increment is a special feature supported by the LP3943 to eliminate repeated chip and register addressing

when data are to be written to or read from registers in sequential order. The auto increment bit is inside the

register address byte, as shown in Figure 6-6. Auto increment is enabled when this bit is programmed to “1” and

disabled when it is programmed to “0”.

Bits 5, 6 and 7 in the register address byte must always be zero.

Figure 6-6. Register Address Byte

In the READ mode, when auto increment is enabled, I2C master could receive any number of bytes from LP3943

without selecting chip address and register address again. Every time the I2C master reads a register, the

LP3943 increments the register address, and the next data register is read. When I2C master reaches the last

register (09H), the register address rolls over to 00H.

In the WRITE mode, when auto increment is enabled, the LP3943 increments the register address every time

I2C master writes to register. When the last register (09H register) is reached, the register address rolls over to

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LP3943

SNVS256E – NOVEMBER 2003 – REVISED OCTOBER 2024

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