AHB bus in stm32_ Apb2 bus_ Apb1 bus what are these

What is? APB Bus

　　APB（Advanced Peripheral Bus）, Peripheral bus means . The bus protocol is ARM The company put forward AMBA One of the bus structures , It has almost become a standard on-chip bus structure .APB It is mainly used for the connection between peripheral peripherals with low bandwidth , for example UART、1284 etc. , Its bus architecture is not like AHB Support multiple main modules , stay APB The only main module inside is APB Bridge . Its features include ： Two The clock Periodic transmission ; No need to wait for cycles and response signals ; The control logic is simple , There are only four control signals .APB The transmission on can be illustrated by the state diagram shown in the figure .

　　APB It is mainly used for the connection between peripheral peripherals with low bandwidth , for example UART、1284 etc. , Its bus architecture is not like AHB Support multiple main modules , stay APB The only main module inside is APB Bridge . Its features include ： Two clock cycles transmit ; No need to wait for cycles and response signals ; The control logic is simple , There are only four control signals .APB The transmission on can be illustrated by the state diagram shown in the figure .

　　

　　STM32 in AHB Bus

　　AHB, yes Advanced High performance Bus Abbreviation , High performance bus , This is a kind of “ The system bus ”.AHB Mainly used for high performance modules （ Such as CPU、DMA and DSP etc. ） Connection between .

　　AHB The system consists of a main module 、 From modules and infrastructure （Infrastructure）3 Part of it is made up of , Whole AHB The transmission on the bus is sent by the main module , The slave module is responsible for responding .

　　 Corresponding to a register , We can use C Language pointer to address and modify the contents of this address , So as to modify the contents of this register .

　　 It is precisely because there are various registers and I/O Address mapping of ports , We can be here 51 Single chip microcomputer

　　 Easy to use in the program P2^0 =0xFF; TMOD =0xFF Wait for the assignment sentence to configure the register , So as to control the single chip microcomputer .

　　 In fact, the address bus is used to store addresses ,Cortex-M3 The address mapping of is similar ,Cortex-M3 Yes 32 Root address line , So its addressing space size is 2^32

　　bit=4GB.（ Here what 32 There is no need to tangle with the address line , Just know that the configuration is 4G The address is OK ）

　　APB2 What is a bus

　    APB2 Bus refers to a specific segment of address , Such as ：0x4001 0000—XXXX

　　APB1 Bus what these are

　　 Computer Hardware devices have lines to transmit data and addresses , Some computer data lines and address lines are public , We should adopt the time-sharing method , Some computers have fewer actual address lines than The integrated circuit Number of address lines , It is necessary to adopt segmented addressing .

　　 Because we need to share , So it's called bus （bus） There are data bus and address bus .

　　 The bus has a control bus , Data bus and address bus , The control bus sends control signals , The address bus transmits address signals ,CPU To access memory , You must first give the address of the memory on the address bus , So-called 32 The address bus of bit refers to root CPU The connected address lines are 32 strip , Each one can give two different symbols （0 and 1） Then you can access 2 Of 32 Power space memory . Data bus is used to transmit data ,CPU To read data from memory or cache , It must be done through the data bus ,32 The data bus of bit corresponds to CPU Connected 32 Data line . A data line transmits a binary number ,32 Bit data bus can be transmitted once 2 Bytes of data .

　　CPU The bit in refers to CPU The ability to process data at one time ,32 position CPU It can be dealt with at one time 32 A data ,64 position CPU It can be dealt with at one time 64 A data .

　　64 position CPU Not necessarily 64 Bit data bus and address bus , If it is 32 Bit bus , It can be transmitted in two times , Generally, the number of bits of the bus is greater than or equal to CPU Number of digits .