UM10208_2
© NXP B.V. 2007. All rights reserved.
User manual
Rev. 02 — 1 June 2007
194 of 362
NXP Semiconductors
UM10208
Chapter 16: LPC2800 I
2
C
4.
Pin description
5.
I
2
C operating modes
In a given application, the I
2
C interface may operate as a master, a slave, or both. In the
slave mode, the I
2
C hardware looks for its slave address and the general call address. If
one of these addresses is detected, an interrupt is requested. If the processor wishes to
become the bus master, the hardware waits until the bus is free before it enters master
mode, so that current operation is not disrupted. If the I
2
C interface loses bus arbitration
during the address/direction byte, it switches to the slave mode immediately and can
detect its slave address or the broadcast address in the address/direction byte.
5.1 Master Transmit mode
In this mode data is transmitted from the LPC288x I
2
C interface to a slave device.
The first byte written to the Tx FIFO is transmitted after a Start condition. It contains the
slave address of the receiving device (7 bits) and 0 in the data direction bit to indicate that
data will flow from master to slave. After each byte is transmitted, the I
2
C interface
samples an acknowledge bit from the slave. Start and Stop conditions are output to
indicate the beginning and end of frames.
If the interface loses bus arbitration to another master during the address/direction byte, it
will check the address/direction byte for a match with its slave address or the broadcast
address, and automatically enter slave transmit or slave receive mode if there’s a match.
Fig 26. I
2
C bus configuration
OTHER DEVICE WITH
I
2
C INTERFACE
pull-up
resistor
OTHER DEVICE WITH
I
2
C INTERFACE
LPC288x
SDA
SCL
I
2
C bus
SCL
SDA
pull-up
resistor
Table 214. I
2
C Pin Description
Pin
Type
Description
SDA
Input/Output
I
2
C Serial Data
SCL
Input/Output
I
2
C Serial Clock