BS85B12-3 HOLTEK [Holtek Semiconductor Inc], BS85B12-3 Datasheet - Page 130

• Manufacturer Part Number: BS85B12-3
• Description: Touch Key Flash Type 8-Bit MCU with LCD/LED Driver
• Manufacturer: HOLTEK [Holtek Semiconductor Inc]

Rev. 1.00
I
I
2
2
C Bus Slave Address Acknowledge Signal
C Bus Data and Acknowledge Signal
After the master has transmitted a calling address, any slave device on the I
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 to
HTX bit in the SIMC1 register should be set to 0 .
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, 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
transmitter, the slave device must first write the data to be transmitted into the SIMD register. If setup
as a receiver, the slave device must read the transmitted data from the SIMD 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 setup as a transmitter will check the RXAK bit in the
SIMC1 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.
1 . If the SRW flag is low, then the microcontroller slave device should be setup as a receiver and the
Touch Key Flash MCU with LCD/LED Driver
2
C Bus. The corresponding data will be stored in the SIMD register. If setup as a
I
2
C Bus ISR Flow Chart
124
BS85B12-3/BS85C20-3
2
C bus, whose own internal
February 1, 2011