Rev. 1.50
140
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Rev. 1.50
141
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HT66F0175/HT66F0185
A/D Flash MCU with EEPROM
HT66F0175/HT66F0185
A/D Flash MCU with EEPROM
Bit 0
RXAK
: I
2
C bus receive acknowledge flag
0: Slave receives acknowledge flag
1: Slave does not receive acknowledge flag
The RXAK flag is the receiver acknowledge flag. When the RXAK flag is “0”, it
means that a acknowledge signal has been received at the 9th clock, after 8 bits of data
have been transmitted. When the slave device in the transmit mode, the slave device
checks the RXAK flag to determine if the master receiver wishes to receive the next
byte. The slave transmitter will therefore continue sending out data until the RXAK
flag is “1”. When this occurs, the slave transmitter will release the SDA line to allow
the master to send a STOP signal to release the I
2
C Bus.
I
2
C Bus Communication
Communication on the I
2
C bus requires four separate steps, a START signal, a slave device address
transmission, a data transmission and finally a STOP signal. When a START signal is placed on
the I
2
C bus, all devices on the bus will receive this signal and be notified of the imminent arrival of
data on the bus. The first seven bits of the data will be the slave address with the first bit being the
MSB. If the address of the slave device matches that of the transmitted address, the HAAS bit in the
SIMC1 register will be set and an I
2
C interrupt will be generated. After entering the interrupt service
routine, the slave device must first check the condition of the HAAS and SIMTOF bits to determine
whether the interrupt source originates from an address match, 8-bit data transfer completion or
I
2
C bus time-out occurrence. During a data transfer, note that after the 7-bit slave address has been
transmitted, the following bit, which is the 8th bit, is the read/write bit whose value will be placed in
the SRW bit. This bit will be checked by the slave device to determine whether to go into transmit or
receive mode. Before any transfer of data to or from the I
2
C bus, the microcontroller must initialise
the bus, the following are steps to achieve this:
• Step 1
Set the SIM2~SIM0 bits to “110” and SIMEN bit to “1” in the SIMC0 register to enable the I
2
C
bus.
• Step 2
Write the slave address of the device to the I
2
C bus address register SIMA.
• Step 3
Set the SIME interrupt enable bit of the interrupt control register to enable the SIM interrupt.
I
2
C Bus Initialisation Flow Chart