參數(shù)資料
型號(hào): 935275617112
廠商: NXP SEMICONDUCTORS
元件分類: 微控制器/微處理器
英文描述: 8 I/O, PIA-GENERAL PURPOSE, PDSO16
封裝: 7.50 MM, LEAD FREE, PLASTIC, MS-013, SOT-162-1, SO-16
文件頁(yè)數(shù): 31/33頁(yè)
文件大?。?/td> 316K
代理商: 935275617112
2002 Nov 22
7
Philips Semiconductors
Product specication
Remote 8-bit I/O expander for I2C-bus
PCF8574
6
CHARACTERISTICS OF THE I2C-BUS
The I2C-bus is for 2-way, 2-line communication between
different ICs or modules. The two lines are a serial data
line (SDA) and a serial clock line (SCL). Both lines must be
connected to a positive supply via a pull-up resistor when
connected to the output stages of a device. Data transfer
may be initiated only when the bus is not busy.
6.1
Bit transfer
One data bit is transferred during each clock pulse. The
data on the SDA line must remain stable during the HIGH
period of the clock pulse as changes in the data line at this
time will be interpreted as control signals (see Fig.5).
6.2
Start and stop conditions
Both data and clock lines remain HIGH when the bus is not
busy. A HIGH-to-LOW transition of the data line, while the
clock is HIGH is defined as the start condition (S).
A LOW-to-HIGH transition of the data line while the clock
is HIGH is defined as the stop condition (P) (see Fig.6).
6.3
System conguration
A device generating a message is a ‘transmitter’, a device
receiving is the ‘receiver’. The device that controls the
message is the ‘master’ and the devices which are
controlled by the master are the ‘slaves’ (see Fig.7).
Fig.5 Bit transfer.
handbook, full pagewidth
MBC621
data line
stable;
data valid
change
of data
allowed
SDA
SCL
Fig.6 Definition of start and stop conditions.
handbook, full pagewidth
MBC622
SDA
SCL
P
STOP condition
SDA
SCL
S
START condition
Fig.7 System configuration.
MBA605
MASTER
TRANSMITTER /
RECEIVER
SLAVE
RECEIVER
SLAVE
TRANSMITTER /
RECEIVER
MASTER
TRANSMITTER
MASTER
TRANSMITTER /
RECEIVER
SDA
SCL
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