BH67F2470 Datasheet, PDF (155/240 Pages) Holtek Semiconductor Inc – Glucose Meter Flash MCU with LCD

BH67F2470
Glucose Meter Flash MCU with LCD
I²C Bus Start Signal
The START signal can only be generated by the master device connected to the I²C bus and not by
the slave device. This START signal will be detected by all devices connected to the I²C bus. When
detected, this indicates that the I²C 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.
Slave Address
The transmission of a START signal by the master will be detected by all devices on the I²C 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 I²C bus
interrupt signal will be generated. The next bit following the address, which is the 8th 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 9th bit. The slave device will also set
the status flag HAAS when the addresses match.
As an I²C bus interrupt can come from three sources, when the program enters the interrupt
subroutine, the HAAS bit and SIMTOF bit 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
I²C communication time-out. When a slave address is matched, the device 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.
I²C Bus Read/Write Signal
The SRW bit in the SIMC1 register defines whether the slave device wishes to read data from the
I²C bus or write data to the I²C 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 I²C bus, therefore the slave device must be setup to send data to the I²C bus as
a transmitter. If the SRW flag is "0" then this indicates that the master wishes to send data to the I²C
bus, therefore the slave device must be setup to read data from the I²C bus as a receiver.
I²C Bus Slave Address Acknowledge Signal
After the master has transmitted a calling address, any slave device on the I²C 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 setup to be a transmitter so the HTX bit in the SIMC1 register
should be set high. If the SRW flag is low, then the microcontroller slave device should be setup as a
receiver and the HTX bit in the SIMC1 register should be cleared to zero.
Rev. 1.00
155
March 15, 2017