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UM10360_0
© NXP B.V. 2009. All rights reserved.
User manual
Rev. 00.06 — 5 June 2009
422 of 808
NXP Semiconductors
UM10360
Chapter 19: LPC17xx I2C0/1/2 interface
I2SCLL and I2SCLH values should not necessarily be the same. Software can set
different duty cycles on SCL by setting these two registers. For example, the I
2
C-bus
specification defines the SCL low time and high time at different values for a Fast Mode
and Fast Mode Plus I
2
C.
9.
Details of I
2
C operating modes
The four operating modes are:
•
Master Transmitter
•
Master Receiver
•
Slave Receiver
•
Slave Transmitter
Data transfers in each mode of operation are shown in
these figures when describing the I
2
C operating modes.
to
, circles are used to indicate when the serial interrupt flag
is set. The numbers in the circles show the status code held in the I2STAT register. At
these points, a service routine must be executed to continue or complete the serial
transfer. These service routines are not critical since the serial transfer is suspended until
the serial interrupt flag is cleared by software.
When a serial interrupt routine is entered, the status code in I2STAT is used to branch to
the appropriate service routine. For each status code, the required software action and
details of the following serial transfer are given in tables from
9.1 Master Transmitter mode
In the master transmitter mode, a number of data bytes are transmitted to a slave receiver
(see
). Before the master transmitter mode can be entered, I2CON must be
initialized as follows:
Table 375. Abbreviations used to describe an I
2
C operation
Abbreviation
Explanation
S
START condition
SLA
7-bit slave address
R
Read bit (HIGH level at SDA)
W
Write bit (LOW level at SDA)
A
Acknowledge bit (LOW level at SDA)
A
Not acknowledge bit (HIGH level at SDA)
Data
8-bit data byte
P
STOP condition
Sr
Repeated START condition