4
Philips Semiconductors
The I
2
C-bus specification
2THE I
2
C-BUS BENEFITS DESIGNERS AND
MANUFACTURERS
In consumer electronics, telecommunications and
industrial electronics, there are often many similarities
between seemingly unrelated designs. For example,
nearly every system includes:
• Some intelligent control, usually a single-chip
microcontroller
• General-purpose circuits like LCD drivers, remote I/O
ports, RAM, EEPROM, or data converters
• Application-oriented circuits such as digital tuning and
signal processing circuits for radio and video systems, or
DTMF generators for telephones with tone dialling.
To exploit these similarities to the benefit of both systems
designers and equipment manufacturers, as well as to
maximize hardware efficiency and circuit simplicity, Philips
developed a simple bi-directional 2-wire bus for efficient
inter-IC control. This bus is called the Inter IC or I
2
C-bus.
At present, Philips’ IC range includes more than 150
CMOS and bipolar I
2
C-bus compatible types for
performing functions in all three of the previously
mentioned categories. All I
2
C-bus compatible devices
incorporate an on-chip interface which allows them to
communicate directly with each other via the I
2
C-bus. This
design concept solves the many interfacing problems
encountered when designing digital control circuits.
Here are some of the features of the I
2
C-bus:
• Only two bus lines are required; a serial data line (SDA)
and a serial clock line (SCL)
• Each device connected to the bus is software
addressable by a unique address and simple
master/slave relationships exist at all times; masters can
operate as master-transmitters or as master-receivers
• It’s a true multi-master bus including collision detection
and arbitration to prevent data corruption if two or more
masters simultaneously initiate data transfer
• Serial, 8-bit oriented, bi-directional data transfers can be
made at up to 100 kbit/s in the Standard-mode, up to
400 kbit/s in the Fast-mode, or up to 3.4 Mbit/s in the
High-speed mode
• On-chip filtering rejects spikes on the bus data line to
preserve data integrity
• The number of ICs that can be connected to the same
bus is limited only by a maximum bus capacitance of
400 pF.
Figure 1 shows two examples of I
2
C-bus applications.
2.1 Designer benefits
I
2
C-bus compatible ICs allow a system design to rapidly
progress directly from a functional block diagram to a
prototype. Moreover, since they ‘clip’ directly onto the
I
2
C-bus without any additional external interfacing, they
allow a prototype system to be modified or upgraded
simply by ‘clipping’ or ‘unclipping’ ICs to or from the bus.
Here are some of the features of I
2
C-bus compatible ICs
which are particularly attractive to designers:
• Functional blocks on the block diagram correspond with
the actual ICs; designs proceed rapidly from block
diagram to final schematic.
• No need to design bus interfaces because the I
2
C-bus
interface is already integrated on-chip.
• Integrated addressing and data-transfer protocol allow
systems to be completely software-defined
• The same IC types can often be used in many different
applications
• Design-time reduces as designers quickly become
familiar with the frequently used functional blocks
represented by I
2
C-bus compatible ICs
• ICs can be added to or removed from a system without
affecting any other circuits on the bus
• Fault diagnosis and debugging are simple; malfunctions
can be immediately traced
• Software development time can be reduced by
assembling a library of reusable software modules.
In addition to these advantages, the CMOS ICs in the
I
2
C-bus compatible range offer designers special features
which are particularly attractive for portable equipment and
battery-backed systems.
They all have:
• Extremely low current consumption
• High noise immunity
• Wide supply voltage range
• Wide operating temperature range.
zj8807252013-12-04英文原版，可以锻炼英语
linchuanzhi_8862018-08-10感谢分享，学习一下
