140
Philips Semiconductors
Preliminary User Manual
LPC2119/2129/2292/2294
ARM-based Microcontroller
Figure 29: Format of slave receiver mode
Slave Transmitter Mode:
The first byte is received and handled as in the slave receiver mode. However, in this mode, the direction bit will indicate that the
transfer direction is reversed. Serial data is transmitted via SDA while the serial clock is input through SCL. START and STOP
conditions are recognized as the beginning and end of a serial transfer. In a given application, I
2
C may operate as a master and
as a slave. In the slave mode, the I
2
C hardware looks for its own slave address and the general call address. If one of these
addresses is detected, an interrupt is requested. When the microcontroller wishes to become the bus master, the hardware waits
until the bus is free before the master mode is entered so that a possible slave action is not interrupted. If bus arbitration is lost
in the master mode, I
2
C switches to the slave mode immediately and can detect its own slave address in the same serial transfer.
Figure 30: Format of slave transmitter mode
PIN DESCRIPTION
Table 101: I2C Pin Description
Pin Name
Type
Description
SDA
Input/
Output
Serial Data.
I
2
C data input and output. The associated port pin has an open drain output in
order to conform to I
2
C specifications.
SCL
Input/
Output
Serial Clock.
I
2
C clock input and output. The associated port pin has an open drain output in
order to conform to I
2
C specifications.
"0" - Write
"1" - Read
Data Transferred
(n Bytes + Acknowledge)
From Master to Slave
From Slave to Master
A = Acknowledge (SDA low)
A = Not Acknowledge (SDA high)
S = START condition
P = STOP Condition
RS = Repeated START Condition
S
Slave Address
W
DATA
A
DATA
P/RS
A/A
A
"0" - Write
"1" - Read
Data Transferred
(n Bytes + Acknowledge)
From Master to Slave
From Slave to Master
A = Acknowledge (SDA low)
A = Not Acknowledge (SDA high)
S = START condition
P = STOP Condition
S
Slave Address
R
DATA
A
DATA
P
A
A