I2C bus Learning (III)-addressing

Addressing of Bus

(1) Definition of addressing byte

I2C bus uses 7-bit addressing bytes, which are the first byte after the starting signal.

D7 ~ The address of the slave machine composed of D1 bits. D0 is the data transmission direction. If it is set to "0", it indicates that the host writes data to the slave database. If it is set to "1", it indicates that the Host reads data from the slave database.

(2) Addressing

When the host sends the address, each slave on the bus uses the seven-bit address code with its own address. For comparisonIf they are the same, they are considered to be being addressed by the host, and are identified as senders or receivers according to the R/bit. The slave address consists of a fixed part and a programmable part.. In a system, you may want to access multiple identical slaves. The programmable part of the slave address determines the maximum number of devices that can access the bus. For example, if a slave has four fixed and three programmable positions, only eight identical devices can be addressable, eight identical devices can be connected to the I2C bus system.

(3) special addresses in addressing bytes

Fixed address numbers 0000 and 1111 have been reserved for special purposes.

In special cases, 00000000 "is called a universal call address. The general call address is described in the second byte. Format: for example, when the second byte is 06h, all slave devices that can respond to the universal call address are reset and hardware is loaded into the programmable part of the slave address. When the slave device that can respond to the command is reset, the SDA and SCL lines are not lowered to avoid blocking the bus.