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Rev. 1.00
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Standard 8051 8-Bit Flash MCU
HT85F2260/HT85F2270/HT85F2280
I2C Serial Interface
I2C Serial Interface
I
2
C Bus Data and Acknowledge Signal
The transmitted data is 8-bits wide and is transmitted after the slave device has acknowledged
receipt of its slave address. The order of serial bit transmission is the MSB first and the LSB last.
After receipt of 8-bits of data, the receiver must transmit an acknowledge signal, a low level, before
it can receive the next data byte. If the slave transmitter does not receive an acknowledge bit signal
from the master receiver, then the slave transmitter will release the SDA line to allow the master to
send a STOP signal to release the I
2
C Bus. The corresponding data will be stored in the I2CDAT
register. If setup as a transmitter, the slave device must first write the data to be transmitted into
the I2CDAT register. If setup as a receiver, the slave device must read the transmitted data from the
I2CDAT register.
The AA bit in the I2CCON register bit indicates the type of acknowledge returned during the
acknowledge cycle on the SCL pin. If this bit is cleared to zero, a "not acknowledge" (high level
on SDA) is returned during the acknowledge cycle. If the bit is set to high, an "acknowledge" (low
level on SDA) is returned during the acknowledge cycle. The slave device, which is setup as a
transmitter will check the AA bit in the I2CCON register to determine if it is to send another data
byte, if not then it will release the SDA line and await the receipt of a STOP signal from the master.
Note:
* When a slave add�ess is matched� the device m�st be placed in eithe� the t�ansmit mode
and then w�ite data to the I�CDAT �egiste�� o� in the �eceive mode whe�e it m�st implement a
d�mm� �ead f�om the I�CDAT �egiste� to �elease the SCL line.
I
2
C Communication Timing Diagram