Introduction
This article is written to explain about reset in microcontroller and its types. The 8051 microcontrollers in a programmable device used to perform various operation like machine automation control system and mini and major projects in universities. When a microcontroller in performing an operation or after completion of operation, reset option may require there. Reset of a microcontroller may be required to stop immediately (abort present operation) (or) initialize the microcontroller to default value. It is important to note that, the reset option will not erase the program stored in micro controllers.
Definition of reset
Reset in 8051 microcontroller is an operation to reset all operation , clears register value and set to it initialize mode.
To reset microcontroller RESET (Pin No: 9) must be active high at least two machine cycle.
Types of Reset in 8051 microcontrollers
There are two types of reset available in micro controller
- Power ON reset
- Reset by push button
1. Power ON reset
When we start system, it is required to abort incomplete data stored in memory register. So, it may lead to continue the operation which stopped during previous time. So, a reset circuit connected with RESET pin. A resistor 8.2 K ohm connected through ground potential and a 10 micro farad capacitor connected through +5V dc source. This circuit maintains at least two active high input to reset micro controller.
2. Reset by push button
This reset by push button is required whenever one who wants breaks current operation. To do so, reset push button, which connected parallel to the 10 micro farad capacitors must be pressed , till RESET pin of microcontroller get at least two machine cycle.
Reset Operation
After reset operation of micro controller’s program counter will be cleared and starts to execute from register address #00H. Further register bank #0 will be selected as default. Stack pointer will be initialized from address 07H. All ports (P0,P1,P2,P3) will become as input ports.
