Inter-integrated circuit (I2C) interface
RM0365
799/1080
DocID025202 Rev 7
28.4.10 SMBus specific features
This section is relevant only when SMBus feature is supported. Please refer to
Introduction
The System Management Bus (SMBus) is a two-wire interface through which various
devices can communicate with each other and with the rest of the system. It is based on I
2
C
principles of operation. SMBus provides a control bus for system and power management
related tasks.
This peripheral is compatible with the SMBUS specification rev 2.0 (http://smbus.org).
The System Management Bus Specification refers to three types of devices.
•
A slave is a device that receives or responds to a command.
•
A master is a device that issues commands, generates the clocks and terminates the
transfer.
•
A host is a specialized master that provides the main interface to the system’s CPU. A
host must be a master-slave and must support the SMBus host notify protocol. Only
one host is allowed in a system.
1. SCL period t
SCL
is greater than t
SCLL
+ t
SCLH
due to SCL internal detection delay. Values provided for t
SCL
are examples
only.
2. t
SYNC1 +
t
SYNC2
minimum value is 4 x t
I2CCLK
= 250 ns. Example with t
SYNC1 +
t
SYNC2
= 1000 ns
3. t
SYNC1 +
t
SYNC2
minimum value is 4 x t
I2CCLK
= 250 ns. Example with t
SYNC1 +
t
SYNC2
= 750 ns
4. t
SYNC1 +
t
SYNC2
minimum value is 4 x t
I2CCLK
= 250 ns. Example with t
SYNC1 +
t
SYNC2
= 500 ns
Table 143. Examples of timings settings for f
I2CCLK
= 48 MHz
Parameter
Standard-mode (Sm)
Fast-mode (Fm)
Fast-mode Plus (Fm+)
10 kHz
100 kHz
400 kHz
1000 kHz
PRESC
0xB
0xB
5
5
SCLL
0xC7
0x13
0x9
0x3
t
SCLL
200 x 250 ns = 50 µs
20 x 250 ns = 5.0 µs
10 x 125 ns = 1250 ns
4 x 125 ns = 500 ns
SCLH
0xC3
0xF
0x3
0x1
t
SCLH
196 x 250 ns = 49 µs
16 x 250 ns = 4.0 µs
4 x 125 ns = 500 ns
2 x 125 ns = 250 ns
t
SCL
(1)
~100 µs
(2)
~10 µs
~2500 ns
(3)
~875 ns
(4)
SDADEL
0x2
0x2
0x3
0x0
t
SDADEL
2 x 250 ns = 500 ns
2 x 250 ns = 500 ns
3 x 125 ns = 375 ns
0 ns
SCLDEL
0x4
0x4
0x3
0x1
t
SCLDEL
5 x 250 ns = 1250 ns
5 x 250 ns = 1250 ns
4 x 125 ns = 500 ns
2 x 125 ns = 250 ns
1. The SCL period t
SCL
is greater than t
SCLL
+ t
SCLH
due to the SCL internal detection delay. Values provided for t
SCL
are only
examples.
2. t
SYNC1 +
t
SYNC2
minimum value is 4x t
I2CCLK
= 83.3 ns. Example with t
SYNC1 +
t
SYNC2
= 1000 ns
3. t
SYNC1 +
t
SYNC2
minimum value is 4x t
I2CCLK
= 83.3 ns. Example with t
SYNC1 +
t
SYNC2
= 750 ns
4. t
SYNC1 +
t
SYNC2
minimum value is 4x t
I2CCLK
= 83.3 ns. Example with t
SYNC1 +
t
SYNC2
= 250 ns