I 2 C Interface - Holtek HT66F20 Manual

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.
There are several configuration options associated with the I
the function which selects the SIM pins rather than normal I/O pins. Note that if the configuration
option does not select the SIM function then the SIMEN bit in the SIMC0 register will have no
effect. A configuration option determines the debounce time of the I
system clock to in effect add a debounce time to the external clock to reduce the possibility of
glitches on the clock line causing erroneous operation. The debounce time, if selected, can be
chosen to be either 2 or 4 system clocks. To achieve the required I
exists a relationship between the system clock, f
Standard or Fast mode operation, users must take care of the selected system clock frequency and
the configured debounce time to match the criterion shown in the following table.
I C Debounce Time Selection
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No debo�nce
2 system clock debo�nce
4 system clock debo�nce
Rev. 2.50
HT66F20/HT66F30/HT66F40/HT66F50/HT66F60
HT66FU30/HT66FU40/HT66FU50/HT66FU60
A/D Flash MCU with EEPROM
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 is identified by a unique address which
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C bus.
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, and the I
SYS
I C Standard Mode (100kHz)
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f > 2MHz
SYS
f > 4MHz
SYS
f > 8MHz
SYS
I C Minimum f Frequency
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SYS
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V D D
S D A
S C L
D e v i c e
S l a v e
C bus, one is known as the
2
C bus, the slave transmit
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C interface. One of these is to enable
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C interface. This uses the
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C data transfer speed, there
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C debounce time. For either the I
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I C Fast Mode (400kHz)
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f > 5MHz
SYS
f > �0MHz
SYS
f > 20MHz
SYS
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C
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