Introduction PIC controllers are a family of small risc controllers used in embeddeded applications. This growth has made the PICmicro architecture one of the top three architectures available in the general market today.
Instruction ROM is 24 bits wide. Software can access ROM in bit words, where even words hold the least significant 16 bits of each instruction, and odd words hold the most significant 8 bits. The high half of odd words reads as zero. The program counter is 23 bits wide, but the least significant bit is always 0, so there are 22 modifiable bits.
Instructions come in two main varieties, with most important operations add, xor, shifts, etc. The first is like the classic PIC instructions, with an operation between a specified f register i.
The W registers are memory-mapped. The second form is more conventional, allowing three operands, which may be any of 16 W registers. The destination and one of the sources also support addressing modes, allowing the operand to be in memory pointed to by a W register.
The PIC32 architecture brought a number of new features to Microchip portfolio, including: Separate code and data spaces Harvard architecture.
A small number of fixed-length instructions Most instructions are single-cycle 2 clock cycles, or 4 clock cycles in 8-bit modelswith one delay cycle on branches and skips One accumulator W0the use of which as source operand is implied i.
There is no distinction between memory space and register space because the RAM serves the job of both memory and registers, and the RAM is usually just referred to as the register file or simply as the registers.
Special-purpose control registers for on-chip hardware resources are also mapped into the data space. The addressability of memory varies depending on device series, and all PIC devices have some banking mechanism to extend addressing to additional memory. Later series of devices feature move instructions, which can cover the whole addressable space, independent of the selected bank.
In earlier devices, any register move had to be achieved through the accumulator. External data memory is not directly addressable except in some PIC18 devices with high pin count. In general, there is no provision for storing code in external memory due to the lack of an external memory interface.
However, the unit of addressability of the code space is not generally the same as the data space. In contrast, in the PIC18 series, the program memory is addressed in 8-bit increments byteswhich differs from the instruction width of 16 bits. In order to be clear, the program memory capacity is usually stated in number of single-word instructions, rather than in bytes.
Stacks[ edit ] PICs have a hardware call stackwhich is used to save return addresses. The hardware stack is not software-accessible on earlier devices, but this changed with the 18 series devices.
Hardware support for a general-purpose parameter stack was lacking in early series, but this greatly improved in the 18 series, making the 18 series architecture more friendly to high-level language compilers. The instruction set includes instructions to perform a variety of operations on registers directly, the accumulator and a literal constant or the accumulator and a registeras well as for conditional execution, and program branching.
Some operations, such as bit setting and testing, can be performed on any numbered register, but bi-operand arithmetic operations always involve W the accumulatorwriting the result back to either W or the other operand register.
To load a constant, it is necessary to load it into W before it can be moved into another register. On the older cores, all register moves needed to pass through W, but this changed on the "high-end" cores.
PIC cores have skip instructions, which are used for conditional execution and branching. The skip instructions are "skip if bit set" and "skip if bit not set".
Because cores before PIC18 had only unconditional branch instructions, conditional jumps are implemented by a conditional skip with the opposite condition followed by an unconditional branch.
Skips are also of utility for conditional execution of any immediate single following instruction. It is possible to skip instructions. The 18 series implemented shadow registers, registers which save several important registers during an interrupt, providing hardware support for automatically saving processor state when servicing interrupts.
In general, PIC instructions fall into five classes:PIC ® and AVR ® 8-bit microcontrollers allow developers of all skill levels to easily bring their ideas to life.
The combination of easily customizable peripherals and the industry's most code-efficient architectures enable you to bring multiple functions to a single chip with minimal programming.
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DSA-page 1 MPLAB® XC8 Getting Started Guide This document provides a starting point for programmers who are just starting out with. This Instructable will be about designing a music player from using various building blocks.
You will understand the communication between the microcontroller, memory, computer, LCD display, RTC, IR remote, and the music file decoder. Real Time Clock Design (FREE): A Free and Complete RTC design using the DS and a PIC micro (16F88) also re-targetable. This PIC project uses an I2C Clock chip and 7-segment display to create a four digit standard desk clock.