PyQdeck LogoPyQdeckSubjectsSyllabusBlog
Back to the 2023 paper

Module 2: The 8051 Architecture

20237m

Explain the special function registers associated with the I/O Ports. How to configure an I/O port as an input pin?

Search GoogleAsk AI
Worked SolutionAI Assisted

SFRs Associated with I/O Ports & Input Configuration

  • Port Latches: P0 (80H), P1 (90H), P2 (A0H), P3 (B0H) – each bit latch + driver with pull-up (P0 open-drain).

Input Configuration: 8051 ports are quasi-bidirectional. To configure pin as input:

  1. Write 1 to latch: MOV P1,#0FFH or SETB P1.3 makes FET off, pull-up holds high, external can drive low/high.
  2. Read pin: MOV A,P1 reads pin state (not latch). If alternative function enabled, direction auto.

Example:

MOV P1,#0FFH ; P1 input
MOV A,P1 ; read
ANL A,#01H
JNZ NOT_PRESSED

Alternative functions selected via SFR controls (SCon, TCon etc.) override I/O.

Similar questions

MICROPROCESSORSDiscuss the Functions associated to all I/O Port pins in 8051.20247mMICROPROCESSORSExplain the Special Function Registers used in 8051.20257mMICROPROCESSORSList the special function register associated with (i) Interrupts (ii) I/O ports (iii) Timers/Counters20217mMICROPROCESSORSExplain serial ports of 8051 microcontroller. Also discuss about registers used in serial communications.20227m
PreviousExplain the following instructions: (i) CJNE (ii) DJNZNextWhat are the special function registers associated with the interrupt module of 8051?
Free AppAndroid App

Coursify Android App

Generate AI courses, take quick quizzes between classes, and master complex engineering concepts on the go.

Install Coursify