M. Amer Iqbal Qureshi
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- Điều hướng trang này:
- General Organization of PIC Microcontrollers
| The PIC Microcontroller
Although microcontrollers were being developed since early 1970’s real boom came in mid 1990’s. A company named Microchip® made its first simple microcontroller, which they called PIC. Originally this was developed as a supporting device for PDP computers to control its peripheral devices, and therefore named as PIC, Peripheral Interface Controller. Thus all the chips developed by Microchip® have been named as a class by themselves and called PIC. Microchip® itself does not use this term anymore to describe their microcontrollers, however use PIC as part of product name. they call their products MCU’s. A large number of microcontroller designs are available from microchip. Depending upon the architecture, memory layout and processing power. They have been classified as low range, mid range, high range and Teach Yourself PIC Microcontrollers | www.electronicspk.com | 10 now digital signal processing microcontrollers. The beauty of these devices is their easy availability, low cost and easy programming and handling. This has made PIC microcontrollers as the apple of hobbyists and students eyes. We shall be talking about mid-range PIC microcontrollers, and use PIC18F452 as a prototype in this manual to explore them. Knowledge gained by learning and exploring one microcontroller is almost 90% applicable on other microcontrollers of the same family. The only difference is in availability of resources on different chips. General Organization of PIC Microcontrollers Although we shall talk in detail on various aspects of these chips in relevant sections, here I would like to give a brief introduction on the overall business involved. Fig-2 shows the pin out details of a very popular 40-pin PIC microcontroller, PIC16F877. as you can see that each pin has been assigned a number of functions. Sometimes two and sometimes three. This situation is very common in microcontrollers, as there is always more which your microcontroller can offer, yet the number of pins on a given package is limited. In a given circuit/application a pin is usually tied to a specific job, and all functionality of a pin is usually not required, however you make opt to use the specific pin your own way. The specific function of a pin is selected by configuring various bits of internal registers. The number and names of these special function registers (SFRs) vary from device to device as some devices have limited functionality while others have more. Nevertheless if we are talking about a function which is present in both devices, its SFR will be same. The selection and settings of these SFR’s is the key to successful programming. It is therefore mandatory to go through the data sheets of the device before starting a project. Second important thing to know is that the devices with same number of pins (from microchip®), are all pin-compatible. Which means if you design a project for 40 pin PIC microcontroller, and later want to replace the chip with another 40 pin PIC the pins are all compatible. It is also good to know that a pin labeled as lets say RB0 is located on pin 33 of PIC 16F877, but the same pin is available on pin 6 in 18 pin PIC16F628. the pins are functionally same, as long as their names are same. So if you develop a project while experimenting on 18F452 using pin RB0, after successful testing you want to transport the project to an 18 pin device, which also has RB0 on it, apart from pin number on package, and recompiling the program, you don have to bother much about anything else. tải về 3.06 Mb. Chia sẻ với bạn bè của bạn:
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