Page 82 - CITS - Electronic Mechanic - TT - 2024
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ELECTRONICS MECHANIC - CITS
Port Registers
8051 microcontrollers have 4 bidirectional I/O ports. Port 0, Port 1, Port 2 and Port 3 (P0, P1, P2 and P3).
Which can work as input or output port. Each port has 8-bits. Hence, a total of 32 input/output pins allows the
microcontroller to communicate with the outside world, which means this port allows it to relate to the peripheral
devices.
PC (Program Counter)
It is a 16-bit register. It is used to hold the address of the memory location from where the next instruction is to be
fetched.
When 8051 initializes PC starts at 0000h and it is automatically is incremented every time after an instruction is
executed. (So, in this way PC maintains the sequence of program execution).
Comparison between 8051 and 8052
Characteristic 8051 8052
RAM 128 bytes 256 bytes
ROM (on-chip) 4 KB 8 KB
Number of Timer 2 3
Interrupt Sources 6 8
Serial Port ce 1 1
Number of I/O Ports 32 32
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CITS : E & H - Electronics Mechanic - Lesson 34 - 42
