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UM10316_0
© NXP B.V. 2008. All rights reserved.
User manual
Rev. 00.06 — 17 December 2008
401 of 571
NXP Semiconductors
UM10316
Chapter 23: LPC2xx I2C-interface
The upper 7 bits are the address to which the I
2
C block will respond when addressed by a
master. If the LSB (GC) is set, the I
2
C block will respond to the general call address
(0x00); otherwise it ignores the general call address.
The I
2
C bus rate settings do not affect the I
2
C block in the slave mode. I2EN must be set
to logic 1 to enable the I
2
C block. The AA bit must be set to enable the I
2
C block to
acknowledge its own slave address or the general call address. STA, STO, and SI must
be reset.
When I2ADR and I2CON have been initialized, the I
2
C block waits until it is addressed by
its own slave address followed by the data direction bit which must be “0” (W) for the I
2
C
block to operate in the slave receiver mode. After its own slave address and the W bit
have been received, the serial interrupt flag (SI) is set and a valid status code can be read
from I2STAT. This status code is used to vector to a state service routine. The appropriate
action to be taken for each of these status codes is detailed in Table 104. The slave
receiver mode may also be entered if arbitration is lost while the I
2
C block is in the master
mode (see status 0x68 and 0x78).
If the AA bit is reset during a transfer, the I
2
C block will return a not acknowledge (logic 1)
to SDA after the next received data byte. While AA is reset, the I
2
C block does not
respond to its own slave address or a general call address. However, the I
2
C bus is still
monitored and address recognition may be resumed at any time by setting AA. This
means that the AA bit may be used to temporarily isolate the I
2
C block from the I
2
C bus.
Table 338. I2C0CONSET and I2C1CONSET used to initialize Slave Receiver mode
Bit
7
6
5
4
3
2
1
0
Symbol
-
I2EN
STA
STO
SI
AA
-
-
Value
-
1
0
0
0
1
-
-