LP3944_14 Datasheet, PDF (8/17 Pages) Texas Instruments – RGB/White/Blue 8-LED Fun Light Driver

LP3944
SNVS264 – MAY 2004
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After the START condition, a chip address is sent by the I²C master. This address is seven bits long followed by
an eighth bit which is a data direction bit (R/W). The LP3944 hardwires bits 7 to 4 and leaves bits 3 to 1
selectable, as shown in Figure 6. For the eighth bit, a “0” indicates a WRITE and a “1” indicates a READ. The
LP3944 supports only a WRITE during chip addressing. The second byte selects the register to which the data
will be written. The third byte contains data to write to the selected register.
Figure 6. Chip Address Byte
ack from slave
ack from slave
ack from slave
start msb Chip Address lsb w ack msb Register Add lsb ack msb DATA lsb ack stop
SCL
SDA
start
id = h'xx
w ack
addr = h'02
w = write (SDA = “0”)
r = read (SDA = “1”)
ack = acknowledge (SDA pulled down by either master or slave)
rs = repeated start
xx = 60 to 67
ack
address h'02
data
Figure 7. LP3944 Register Write
ack stop
However, if a READ function is to be accomplished, a WRITE function must precede the READ function, as
shown in Figure 8.
ack from slave
ack from slave repeated start ack from slave data from slave ack from master
start msb Chip Address lsb w ack msb Register Add lsb ack rs msb Chip Address lsb r ack msb DATA lsb
ack stop
SC
L
SD
A
star
t
id = h'xx
w
ac
k
addr =
h'00
ac r
ks
id = h'xx
r
ac
k
w = write (SDA = “0”)
r = read (SDA = “1”)
ack = acknowledge (SDA pulled down by either master or slave)
rs = repeated start
xx = 60 to 67
Figure 8. LP3944 Register Read
address h'00
data
ac sto
kp
Auto Increment
Auto increment is a special feature supported by the LP3944 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 9. Auto increment is enabled when this bit is programmed to “1” and
disabled when it is programmed to “0”.
8
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