Understanding PIC10F322 Reset and MCLR

The microcontroller features a reset pin known as MCLR, located at pin RA3 or physical pin 8 on a PDIP device. This optional external input can be used to reset the device when needed. Here's a detailed guide on how to manage and utilize the MCLR pin effectively.

MCLR Pin Functionality

The MCLR pin is active low, meaning that bringing this pin to ground will reset the device. This can be useful in various scenarios where a manual or automatic reset is required.

Disabling the MCLR Pin

You have the option to disable the MCLR pin via configuration settings. By setting both MCLRE and LVP configuration bits to 0, the MCLR pin is disabled, and RA3 functions as a standard input pin.

It's important to note that while RA3 can function as an input pin, it is not bi-directional like the other pins on the microcontroller. RA3 can only be configured for input.

Practical Uses for MCLR

When the MCLR pin is enabled, it offers several practical uses:

  • System Initialization: MCLR can be held low to ensure the microcontroller remains in a reset state until other devices in your circuit power up.
  • Manual Reset: A push button can be connected to the MCLR pin to serve as a manual reset. This is particularly useful during development and troubleshooting.

Recommended Circuit for MCLR

Although the datasheet mentions that RA3 is connected to VDD through an internal weak pull-up resistor, it is often beneficial to add an external 10k pull-up resistor for added stability.

For a push button reset:

  • Connect a 10k pull-up resistor between the MCLR pin and VDD.
  • Attach a normally open push button between the MCLR pin and ground.

When the button is pressed, it will complete the circuit to ground, overriding the pull-up resistor and bringing MCLR low, thus resetting the device.

Using RA3 as an Input

If you prefer to use RA3 as a functional input pin rather than a reset, you can disable the MCLR function via configuration settings. In the compiler, you can include the following configuration settings to achieve this:

This disables the MCLR pin, allowing RA3 to be used as a regular input pin for your application needs.

#pragma config MCLRE = OFF // MCLR Pin Function Select bit->MCLR pin function is digital input, MCLR internally tied to VDD
#pragma config LVP = OFF // Low-Voltage Programming

MCLR pin on the PIC10F322

Understanding the functionality and configuration of the MCLR pin on the PIC10F322 microcontroller is crucial for optimizing your project's design and performance. Whether you choose to use MCLR as a reset mechanism or as an additional input pin, proper configuration and circuit design will ensure reliable and efficient operation of your microcontroller.

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