8051 TRAINER KIT
PS-TRAINER-8051 trainer kit is proposed to smooth the progress of learning and developing designs of MCU from Intel and NXP. It has the facility to connect PC’s 101/104 Keyboard, to enter user programs in Assembly languages. Serial communication achieved using 8051. It also supports C & assembly language in standalone kit (P89V51RD2). It’s designed as to facilitate On-board Programmer for NXP 8051 MCU through ISP on serial port.
SWITCH
A switch is an electrical component that can break an electrical circuit, interrupting the current or diverting it from one conductor to another. A switch may be directly manipulated by a human as a control signal to a system, or to control power flow in a circuit.
INTERFACING SWITCH
Fig.1 shows how to interface the switch to microcontroller. A simple switch has an open state and closed state. However, a microcontroller needs to see a definite high or low voltage level at a digital input. A switch requires a pull-up or pull-down resistor to produce a definite high or low voltage when it is open or closed. A resistor placed between a digital input and the supply voltage is called a “pull-up” resistor because it normally pulls the pin’s voltage up to the supply.
INTERFACING SWITCH WITH 8051
We now want to control theLED by using switches in 8051 Trainer Board. It works by turning ON a LED & then turning it OFF when switch is going to LOW or HIGH.
The PS-2 8051 Trainer board has eight numbers of point LEDs, connected with I/O Port lines (P1.0 – P1.7) to make port pins high. Eight switches, connected with I/O port lines (3.0 – P3.7) are used to control eight LEDs.
PIN ASSIGNMENT WITH 8051
CIRCUIT DIAGRAM TO INTERFACE SWITCH WITH 8051
ASSEMBLY PROGRAM TO INTERFACE SWITCH AND LED WITH 8051
| MEMORY ADDRESS | OPCODE | MNEMONICS |
| 8500 | 90 40 03 | MOV DPTR, #4003 |
| 8503 | 74 90 | MOV A, #90 |
| 8505 | F0 | MOVX @DPTR, A |
| 8506 | 90 40 00 | HERE:MOV DPTR, #4000 |
| 8509 | E0 | MOVX A,@DPTR |
| 850A | 90 40 01 | MOV DPTR, #4001 |
| 850D | F0 | MOVX @DPTR, A |
| 850E | 80 FE | SJMP HERE |
SOURCE CODE
The Interfacing switch with 8051 program is very simple and straight forward, that controls LED by using switches when it going LOW or HIGH.
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