tailieunhanh - Interfacing PIC Microcontrollers 29

Interfacing PIC Microcontrollers 29. Explore in detail microcontroller interfacing techniques using the popular PIC 16F877 Work through step-by-step examples interactively using circuit simulation software, supplied as assembly source code Gain the knowledge of a wide range of peripheral devices such as keyboards, displays, sensors and drives and serial communication with other processors, memory and more Use interactive simulation software to design and test circuits. | Interfacing PIC Microcontrollers capability. If necessary current drivers should be added at the latch outputs in the extended system. Other PIC Chips The PIC 16F877 is used throughout this book for simplicity in real applications a chip should be chosen from the PIC range which most closely meets the design requirements both in terms of the absolute number of I O pins and the special interfaces available. In addition the program memory size must be sufficient for the application and the clock speed EEPROM space and so on taken into account. The range is constantly expanding new chips with new features and different combinations of existing features are constantly added. The 16F877 can be used as a reference point when comparing the features of the other chips that are available. The main criteria are Number of I O pins Program memory size Peripheral set Data memory size Instruction set features A small sample has been selected from each series for comparison from the current manufacturers catalogue found at . PIC 16FXXX Mid-range Series The PIC 16FXXX chips all have the same 14-bit instruction set and run at 20 MHz maximum clock rate . A selection of currently available devices is listed in Table a . We can see that the complexity seems to increase with the type number including the number of I O pins memory size and range of peripherals. Most of those listed have been added since the 16F84 and the 16F877 were introduced and many include an internal oscillator which can be used if precise timing is not required. This saves on I O pins and means that all pins except two for the power supply can be allocated to I O devices. The 84A is obsolete for commercial applications where chips are bought in bulk and so the price is now relatively high. It is still used in education as a training device. 266 System Design PIC Small MCUs These include the 10FXXX and 12FXXX devices of which a few examples are listed in Table b for comparison with the .