C Bus Interface - Fujitsu 8FX Hardware Manual

MB95630H Series
2
24.6.1 l

C Bus Interface

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The I C bus interface is an eight-bit serial interface synchronized with the shift
clock.
■ I 2
C System
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The I C bus system uses the serial data line (SDAn) and serial clock line (SCLn) for data
transfers. All the devices connected to the bus require open drain or open collector outputs
which must be connected with a pull-up resistor.
Each of the devices connected to the bus has a unique address which can be set up using
software. The devices always operate in a simple master/slave relationship, where the master
functions as the master transmitter or master receiver. The I
master bus with a collision detection function and arbitration function to prevent data from
being lost if more than one master attempts to start data transfer at the same time.
■ I 2
C Protocol
Figure 24.6-1 shows the format required for data transfer.
MSB
SDAn
SCLn
Start
condition (S)
The slave address is transmitted after a start condition (S) is generated. This address is seven
bits long followed by the data direction bit (R/W) in the eighth bit position. Data is transmitted
after the address. The data is eight bits followed by an acknowledgment.
Data can be transmitted continuously to the same slave address in consecutive units of eight
bits plus acknowledgment.
Data transfer is always ended in the master stop condition (P). However, the repeated start
condition (S) can be used to transmit the address which indicates a different slave without
generating a stop condition.
MN702-00009-2v0-E
Figure 24.6-1 Data Transfer Example
LSB
7-bit address
R/W
Acknowledge bit
FUJITSU SEMICONDUCTOR LIMITED
CHAPTER 24 I
24.6 Operations and Setting Procedure Example
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C bus interface is a true multi-
MSB
8-bit data
No acknowledge
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C BUS INTERFACE
LSB
Stop
condition (P)
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