Nxp Semiconductors UM10237 用户手册

UM10237_2

© NXP B.V. 2008. All rights reserved.

Data transfer from a slave transmitter to a master receiver. The first byte (the slave 
address) is transmitted by the master. The slave then returns an acknowledge bit. 
Next follows the data bytes transmitted by the slave to the master. The master returns 
an acknowledge bit after all received bytes other than the last byte. At the end of the 
last received byte, a “not acknowledge” is returned. The master device generates all 
of the serial clock pulses and the START and STOP conditions. A transfer is ended 
with a STOP condition or with a repeated START condition. Since a repeated START 
condition is also the beginning of the next serial transfer, the I

2

C bus will not be 

released.

Each of the three I

2

C interfaces on the LPC2400 is byte oriented, and has four operating 

modes: master transmitter mode, master receiver mode, slave transmitter mode and 
slave receiver mode.

The three I

2

C interfaces are identical except for the pin I/O characteristics. I

2

C0 complies 

with entire I

2

C specification, supporting the ability to turn power off to the LPC2400 

without causing a problem with other devices on the same I

2

C bus (see "The I

2

C-bus 

specification" description under the heading "Fast-Mode", and notes for the table titled 
"Characteristics of the SDA and SCL I/O stages for F/S-mode I

2

C-bus devices"). This is 

sometimes a useful capability, but intrinsically limits alternate uses for the same pins if the 
I2C interface is not used. Seldom is this capability needed on multiple I2C interfaces 
within the same microcontroller. Therefore, I

2

C1 and I

2

C2 are implemented using 

standard port pins, and do not support the ability to turn power off to the LPC2400 while 
leaving the I

2

C bus functioning between other devices. This difference should be 

considered during system design while assigning uses for the I

2

C interfaces.

 

OTHER DEVICE WITH

I 

2

C INTERFACE

pull-up
resistor

OTHER DEVICE WITH

I 

2

C INTERFACE

SDA

SCL

I 

2

C bus

SCL

SDA

pull-up
resistor