Datasheet

...
USCI Master
USCI Slave
Other Master
Other Slave
...
Bits set or reset by software
Bits set or reset by hardware
1
7 8 7 8
1 1 1 1 1 1 1 1
S Slave Address
R/W
ACK
Data
ACK
S Slave Address
R/W ACK
Data
ACK
P
1 Any
Number
1 Any Number
USCI Operation: I
2
C Mode www.ti.com
Figure 17-7. I
2
C Module Addressing Format with Repeated START Condition
17.3.4 I
2
C Module Operating Modes
In I
2
C mode the USCI module can operate in master transmitter, master receiver, slave transmitter, or
slave receiver mode. The modes are discussed in the following sections. Time lines are used to illustrate
the modes.
Figure 17-8 shows how to interpret the time line figures. Data transmitted by the master is represented by
grey rectangles, data transmitted by the slave by white rectangles. Data transmitted by the USCI module,
either as master or slave, is shown by rectangles that are taller than the others.
Actions taken by the USCI module are shown in grey rectangles with an arrow indicating where in the data
stream the action occurs. Actions that must be handled with software are indicated with white rectangles
with an arrow pointing to where in the data stream the action must take place.
Figure 17-8. I
2
C Time Line Legend
17.3.4.1 Slave Mode
The USCI module is configured as an I
2
C slave by selecting the I
2
C mode with UCMODEx = 11 and
UCSYNC = 1 and clearing the UCMST bit.
Initially the USCI module must to be configured in receiver mode by clearing the UCTR bit to receive the
I
2
C address. Afterwards, transmit and receive operations are controlled automatically depending on the
R/W bit received together with the slave address.
The USCI slave address is programmed with the UCBxI2COA register. When UCA10 = 0, 7-bit addressing
is selected. When UCA10 = 1, 10-bit addressing is selected. The UCGCEN bit selects if the slave
responds to a general call.
When a START condition is detected on the bus, the USCI module will receive the transmitted address
and compare it against its own address stored in UCBxI2COA. The UCSTTIFG flag is set when address
received matches the USCI slave address.
454
SLAU144J–December 2004–Revised July 2013
Universal Serial Communication Interface, I
2
C Mode
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