I 2 C Inte�Face - Holtek HT66F488 Manual

HT66F488/HT66F489
A/D Flash MCU with EEPROM
I C Interface
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The I C interface is used to communicate with external peripheral devices such as sensors,
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EEPROM memory etc. Originally developed by Philips, it is a two line low speed serial interface
for synchronous serial data transfer. The advantage of only two lines for communication, relatively
simple communication protocol and the ability to accommodate multiple devices on the same bus
has made it an extremely popular interface type for many applications.
I C Interface Operation
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The I C serial interface is a two line interface, a serial data line, SDA, and serial clock line, SCL. As
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many devices may be connected together on the same bus, their outputs are both open drain types.
For this reason it is necessary that external pull-high resistors are connected to these outputs. Note
that no chip select line exists, as each device on the I
will be transmitted and received on the I
When two devices communicate with each other on the bidirectional I
master device and one as the slave device. Both master and slave can transmit and receive data,
however, it is the master device that has overall control of the bus. For these devices, which only
operates in slave mode, there are two methods of transferring data on the I
mode and the slave receive mode. The pull-up control function pin-shared with SCL/SDA pin is still
applicable even if I
by its corresponding pull-up control register.
Rev. 1.21
D e v i c e D e v i c e
S l a v e M a s t e r
I C Master Slave Bus Connection
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C bus.
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C device is activated and the related internal pull-up register could be controlled
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S T A R T s i g n a l
f r o m M a s t e r
S e n d s l a v e a d d r e s s
a n d R / W b i t f r o m
A c k n o w l e d g e
f r o m
S e n d d a t a b y t e
f r o m M a s t e r
A c k n o w l e d g e
f r o m
S T O P s i g n a l
f r o m M a s t e r
121
V D D
S D A
S C L
D e v i c e
S l a v e
C bus is identified by a unique address which
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C bus, one is known as the
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C bus, the slave transmit
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M a s t e r
s l a v e
s l a v e
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