Rev. 1.60
166
August 20, 2019
Rev. 1.60
167
August 20, 2019
BS66F340/BS66F350/BS66F360/BS66F370
Touch A/D Flash MCU with LED Driver
BS66F340/BS66F350/BS66F360/BS66F370
Touch A/D Flash MCU with LED Driver
I
2
C Bus Initialisation Flow Chart
• I
2
C Bus Start Signal
The START signal can only be generated by the master device connected to the I
2
C bus and not by
the slave device. This START signal will be detected by all devices connected to the I
2
C bus. When
detected, this indicates that the I
2
C bus is busy and therefore the HBB bit will be set. A START
condition occurs when a high to low transition on the SDA line takes place when the SCL line
remains high.
• I
2
C Slave Address
The transmission of a START signal by the master will be detected by all devices on the I
2
C bus.
To determine which slave device the master wishes to communicate with, the address of the slave
device will be sent out immediately following the START signal. All slave devices, after receiving
this 7-bit address data, will compare it with their own 7-bit slave address. If the address sent out by
the master matches the internal address of the microcontroller slave device, then an internal I
2
C bus
interrupt signal will be generated. The next bit following the address, which is the 8
th
bit, defines the
read/write status and will be saved to the SRW bit of the SIMC1 register. The slave device will then
transmit an acknowledge bit, which is a low level, as the 9
th
bit. The slave device will also set the
status flag HAAS when the addresses match.
As an I
2
C bus interrupt can come from three sources, when the program enters the interrupt
subroutine, the HAAS and SIMTOF bits should be examined to see whether the interrupt source has
come from a matching slave address, the completion of a data byte transfer or the I
2
C bus time-out
occurrence. When a slave address is matched, the devices must be placed in either the transmit mode
and then write data to the SIMD register, or in the receive mode where it must implement a dummy
read from the SIMD register to release the SCL line.