UM10237_2 © NXP B.V. 2008. All rights reserved.
User manual Rev. 02 — 19 December 2008 573 o f 792
NXP Semiconductors UM10237
Chapter 22: LPC24XX I2C interfaces I2C0/1/2
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 I2C bus will not be
released.
Each of the three I2C 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 I2C interfaces are identical except for the pin I/O characteristics. I2C0 complies
with entire I2C specification, supporting the ability to turn power off to the LPC2400
without causing a problem with other devices on the same I2C bus (see "The I2C-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 I2C-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, I2C1 and I2C2 are implemented using
standard port pins, and do not support the ability to turn power off to the LPC2400 while
leaving the I2C bus functioning between other devices. This difference should be
considered during system design while assigning uses for the I2C interfaces.
Fig 111 . I2C bus configuration
OTHER DEVICE WITH
I 2C INTERFACE
pull-up
resistor
OTHER DEVICE WITH
I 2C INTERFACE
LPC2400
SDA SCL
I 2C bus
SCL
SDA
pull-up
resistor