© Koninklijke Philips Electronics N.V. 2006. All rights reserved.
User manual
Rev. 01 — 12 January 2006
132
Philips Semiconductors
UM10161
Volume 1
Chapter 11: I
2
C interfaces
(7)
The values for I2SCLL and I2SCLH 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 400 kHz I
2
C
rate. The value of the register must ensure that the data rate is in the I
2
C data rate range
of 0 through 400 kHz. Each register value must be greater than or equal to 4.
gives some examples of I
2
C-bus rates based on PCLK frequency and I2SCLL and
I2SCLH values.
11.8 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
,
, and
lists abbreviations used in these figures when
describing the I
2
C operating modes.
Table 128: Example I
2
C clock rates
I2SCLH
I
2
C Bit Frequency (kHz) at PCLK (MHz)
1
5
10
16
20
40
60
8
125
10
100
25
40
200
400
50
20
100
200
320
400
100
10
50
100
160
200
400
160
6.25
31.25
62.5
100
125
250
375
200
5
25
50
80
100
200
300
400
2.5
12.5
25
40
50
100
150
800
1.25
6.25
12.5
20
25
50
75
I2C
bitfrequency
PCLK
I2CSCLH
I2CSCLL
+
---------------------------------------------------------
=
Table 129: 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)