Question
Which of the 8051 ports need pull-up resistors to function as an I/O port?
The correct answer is
Port 0
8051 Port 0 Pull-Up Resistors for I/O
The 8051 microcontroller has four 8-bit I/O ports: Port 0, Port 1, Port 2, and Port 3.
Port 0 Specifics:
- Port 0 features an open-drain structure.
- When used as a general-purpose I/O port (either input or output), it requires external pull-up resistors to be connected.
- Without these external pull-ups, the output voltage levels would be undefined (floating) when trying to output a logic HIGH state. The internal FETs can only pull the line LOW effectively.
- Port 0 also serves a dual role as the multiplexed lower address/data bus (AD0-AD7) during external memory access, which also necessitates external pull-ups for the data bus function.
Other Ports:
- Ports 1, 2, and 3 have internal pull-up resistors built-in.
- These ports can function as standard I/O ports with minimal external circuitry.
Therefore, Port 0 is the only port that requires external pull-up resistors for basic I/O functionality.
The correct answer is Port 0.
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Important Questions from Microprocessors and Microcontrollers
Data and address bus width of 8085 microprocessor respectively are
The number of interrupts handled by 8051 microcontroller (other than Reset) is _____.
How many bits are used in the data bus of 8051 ?
16-bit registers consist of:
- The 8051 microcontroller has __________ on-chip RAM and __________ on-chip ROM.
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