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Rev. 1.00
134
October 26, 2018
Rev. 1.00
135
October 26, 2018
BS86DH12C
High Voltage Touch A/D Flash MCU with HVIO
BS86DH12C
High Voltage Touch A/D Flash MCU with HVIO
As an I
2
C bus interrupt can come from three sources, when the program enters the interrupt
subroutine, the HAAS and IICTOF bits should be examined to see whether the interrupt source
has come from a matching slave address or from the completion of a data byte transfer or from the
I
2
C bus time-out occurrence. When a slave address is matched, the device must be placed in either
the transmit mode and then write data to the IICD register, or in the receive mode where it must
implement a dummy read from the IICD register to release the SCL line.
I
2
C Bus Read/Write Signal
The SRW bit in the IICC1 register defines whether the master device wishes to read data from the
I
2
C bus or write data to the I
2
C bus. The slave device should examine this bit to determine if it is to
be a transmitter or a receiver. If the SRW flag is “1” then this indicates that the master device wishes
to read data from the I
2
C bus, therefore the slave device must be set to send data to the I
2
C bus as a
transmitter. If the SRW flag is “0” then this indicates that the master wishes to send data to the I
2
C
bus, therefore the slave device must be set to read data from the I
2
C bus as a receiver.
I
2
C Bus Slave Address Acknowledge Signal
After the master has transmitted a calling address, any slave device on the I
2
C bus, whose
own internal address matches the calling address, must generate an acknowledge signal. The
acknowledge signal will inform the master that a slave device has accepted its calling address. If no
acknowledge signal is received by the master then a STOP signal must be transmitted by the master
to end the communication. When the HAAS flag is high, the addresses have matched and the slave
device must check the SRW flag to determine if it is to be a transmitter or a receiver. If the SRW flag
is high, the slave device should be set to be a transmitter so the HTX bit in the IICC1 register should
be set to “1”. If the SRW flag is low, then the microcontroller slave device should be set as a receiver
and the HTX bit in the IICC1 register should be set to “0”.
I
2
C Bus Data and Acknowledge Signal
The transmitted data is 8-bit 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, level “0”, 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 IICD register. If set
as a transmitter, the slave device must first write the data to be transmitted into the IICD register. If
set as a receiver, the slave device must read the transmitted data from the IICD register.
When the slave receiver receives the data byte, it must generate an acknowledge bit, known as
TXAK, on the 9th clock. The slave device, which is set as a transmitter will check the RXAK bit in
the IICC1 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.