P0 port: The P0 port is a bi-direct

P0 port: The P0 port is a bi-directional 8-bit open I / O port. Each pin can absorb 8TTL gate flow. When the pin on port P1 is written for the first time, it is defined as a high impedance input. P0 can be used for external storage of program dataand can be defined as the eighth data / address bit. During FIASH programming, the P0 port is used as the original code input port. When FIASH doesa check, P0 outputs the original code. At this point, P0 must be pulled to high externally.P1 port: The P1 port is a bi-directional 8-bit I / O port with an internal pull-up resistor. The P1 port buffer can receive and output 4TTL gate current. After pin 1 is written to port P1, it is drawn up internally and can be used as an input. When port P1If the external drive is low, the power is output due to the internal pull-up. Port P1 is received as the eighth address during FLASH programming and verification.P2 port: The P2 port is a bidirectional 8-bit I / O port with an internal pull-up resistor. The P2 port buffer can receive and output 4 TTL gate currents. If the P2 port is written with "1", its pins are pulled internally and pulled up as a resistorInput. And as an input, the P2 port pins are pulled outwards, whereby the current is output. This is due to internal pull-ups. If the P2 port for external program memory or 16-bit external data memory addressduring access, high output port P2 eight address. Given address "1", which uses the internal tensile advantage, feeds the P2 special function portthe contents of the register when eight of the external data memories read and write addresses. The P2 port receives the eight best address signals and control signals during FLASH programming and verification.P3 port: P3 port pins are 8 bidirectional I / O ports with internal pull-up resistors that can receive and output 4 TTL gate currents. When the P1 port writes "1", they are internally moved to a high level and used as an input. Becausethe external pulldown is low, the P3 port outputs the current (ILL) as input. This is due to pullup.The P3 connector can also be used as a special function switch on the AT89C51.