ST QFN20, Руководство пользователя, Страница: 14 / 35

Introduction STCF03
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7.2.4 ADD pin
With this pin it is possible to select one of the 4 possible I²C slave addresses. No internal
pull-up nor pull-down is provided. The pin has to be connected either GND, V
I
, SCL or SDA
to select the desired I²C slave address (see Table 6 )
When ADD is connected to GND the I²C address is assigned automatically while in the
other three configurations in which ADD pin is connected to VBAT or SDA or SCL, the
following procedure must be activated in order that the right address is assigned.
After applying VBAT to the chip, the VBAT voltage must be pulled down to GND for a time
longer than 100 ms. After that time the right I²C address is assigned to the chip. This
procedure must be repeated every time the VBAT voltage is disconnected (see
Figure 4
below)
7.2.5 TMSK pin
This pin can be used to implement the TX masking function. This function has effect only for
flash current settings higher than 200 mA (bit FDIM_3 = 1). Under this condition, when this
pin is pulled high by the P, the current flowing in the LED is forced at 200 mA typ. No internal
pull-up nor pull-down is provided: to be externally wired to GND if TX masking function is not
used.
Table 7. Address table
ADD pin A7 A6 A5 A4 A3 A2 A1 A0
GND 0 1 1 0 0 0 0 R/W
VBAT 0 1 1 0 0 0 1 R/W
SDAL 0 1 1 0 0 1 0 R/W
SCL 0 1 1 0 0 1 1 R/W
Figure 4. Procedure for assigning a non-default I²C address
SDA LINE
A
C
K M
S
B
L
S
B
R
/
W
A
C
K A
C
K A
C
K S
T
O
P M
S
B
M
S
B
L
S
B
L
S
B
DEVICE
ADDRESS
7 bits
W
R
I
T
E
ADDRESS OF
REGISTER
DATA
….
SCL LINE
S
T
A
R
T
VBAT
100ms
Address is assigned.
The new I²C address
can be used for SCL
and SDA
SDA LINE
A
C
K M
S
B
L
S
B
R
/
W
A
C
K A
C
K A
C
K S
T
O
P M
S
B
M
S
B
L
S
B
L
S
B
DEVICE
ADDRESS
7 bits
W
R
I
T
E
ADDRESS OF
REGISTER
DATA
….
SCL LINE
S
T
A
R
T
VBAT
100ms
Address is assigned.
The new I²C address
can be used for SCL
and SDA