embedded general documentation

7/31/2019 Embedded General Documentation

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b) Micro Controller

AT89S52

Features:

8K Bytes of In-System Programmable (ISP) Flash MemoryEndurance: 10,000 Write/Erase Cycles

4.0V to 5.5V Operating Range 256 x 8-bit Internal RAM 32 Programmable I/O Lines Low-power Idle and Power-down Modes Fast Programming Time Flexible ISP Programming (Byte and Page Mode)

Description:

The AT89S52 is a low-power, high-performance CMOS 8-bit microcontroller with 8K bytes ofin-system programmable Flash memory. The device is manufactured using Atmels high-density

nonvolatile memory technology and is compatible with the Indus-try-standard 80C51 instruction

set and pin out. The on-chip Flash allows the program memory to be reprogrammed in-system or

by a conventional nonvolatile memory programmer. By combining a versatile 8-bit CPU with in-

system programmable Flash on a monolithic chip, the Atmel AT89S52 is a powerfulmicrocontroller which provides a highly-flexible and cost-effective solution to many embedded

control applications. The AT89S52 provides the following standard features: 8K bytes of Flash,

256 bytes of RAM, 32 I/O lines, Watchdog timer, two data pointers, three 16-bit timer/counters,a six-vector two-level interrupt architecture, a full duplex serial port, on-chip oscillator, and

clock circuitry. In addition, the AT89S52 is designed with static logic for operation down to zero

frequency and supports two software selectable power saving modes. The Idle Mode stops theCPU while allowing the RAM, timer/counters, serial port, and interrupt system to continue


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functioning. The Power-down mode saves the RAM con-tents but freezes the oscillator,

disabling all other chip functions until the next interrupt or hardware reset.

Memory Organization

MCS-51 devices have a separate address space for Program and Data Memory. Up to

64K bytes each of external Program and Data Memory can be addressed.

(a) Program Memory

If the EA pin is connected to GND, all program fetches are directed to external memory.On the AT89S52, if EA is connected to VCC, program fetches to addresses 0000H through

1FFFH are directed to internal memory and fetches to addresses 2000H through FFFFH are toexternal memory.

(b) Data Memory

The AT89S52 implements 256 bytes of on-chip RAM. The upper 128 bytes occupy a

parallel address space to the Special Function Registers. This means that the upper 128 bytes

have the same addresses as the SFR space but are physically separate from SFR space. When aninstruction accesses an internal location above address 7FH, the address mode used in the

instruction specifies whether the CPU accesses the upper 128 bytes of RAM or the SFR space.

Instructions which use direct addressing access the SFR space. For example, the following directaddressing instruction accesses the SFR at location 0A0H (which is P2).

MOV 0A0H, #data

Instructions that use indirect addressing access the upper 128 bytes of RAM. For example, the

following indirect addressing instruction, where R0 contains 0A0H, accesses the data byte at

address 0A0H, rather than P2 (whose address is 0A0H).

\MOV @R0, #data


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Note that stack operations are examples of indirect addressing, so the upper 128 bytes of data

RAM are available as stack space.

Pin Diagram

c) SOFTWARE DESCRIPTION

INTRODUCTION TO EMBEDDED C:

Ex: Hitecc, Keilc

KEIL Software makes industrial-strength software development tools and C compilers that help

software developers write compact, efficient embedded processor code.

For over two decades Keil Software has delivered the industry's most reliable embedded

software development tools and compilers for writing efficient and compact code to run on the

most popular embedded processors. Used by tens of thousands of customers including General

Motors, Whirlpool, Qualcomm, John Deere and many others, HI-TECH's reliable development


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tools and C compilers, combined with world-class support have helped serious embedded

software programmers to create hundreds of breakthrough new solutions.

Whichever embedded processor family you are targeting with your software, whether it is the

ATMEL, PICC or 8051 series, Keil tools and C compilers can help you write better code and

bring it to market faster.

KEIL PICC is a high-performance C compiler for the Microchip PIC micro

10/12/14/16/17 series of micro controllers. Keil PICC is an industrial-strength ANSI C compiler

- not a subset implementation like some other PIC compilers. The PICC compiler implements

full ISO/ANSI C, with the exception of recursion.

All data types are supported including 24 and 32-bit IEEE standard floating

point. Keil PICC makes full use of specific PIC features and using an intelligent optimizer, can

generate high-quality code easily rivaling hand-written assembler. Automatic handling of page

and bank selection frees the programmer from the trivial details of assembler code.

System Constituents

A Typical Embedded System :


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Technically, there are prevalent and common characteristics of embedded systems.

From a programmer's perspective the following components are minimum: Central

Processing Unit (CPU), Random Access Memory (RAM), Programmable Read Only

Memory (PROM) or Erasable PROM (EPROM), and Input/Output (I/O) space.

(a) Embedded C Compiler:

KEIL C - full featured and portable Reliable - mature, field-proven technology Multiple C optimization levels An optimizing assembler Full linker, with overlaying of local variables to minimize RAM usage Comprehensive C library with all source code provided Includes support for 24-bit and 32-bit IEEE floating point and 32-bit long data types Mixed C and assembler programming Unlimited number of source files Listings showing generated assembler


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Compatible - integrates into the MPLAB IDE, MPLAB ICD and most 3rd-partydevelopment tools

Runs on multiple platforms: Windows, Linux, UNIX, Mac OS X, Solaris

Embedded Development Environment:

PICC can be run entirely from the. This environment allows you to manage all of your

PIC projects. You can compile, assemble and link your embedded application with a single

step. Optionally, the compiler may be run directly from the command line, allowing you to

compile, assemble and link using one command. This enables the compiler to be integrated

into third party development environments, such as Microchip's MPLAB IDE.

(a) Embedded system tools:

Assembler:

An assembler is a computer program for translating assembly language essentially, a

mnemonic representation of machine language into object code. A cross assembler (see cross

compiler) produces code for one type of processor, but runs on another. The computational step

where an assembler is run is known as assembly time. Translating assembly instruction

mnemonics into op-codes, assemblers provide the ability to use symbolic names for memory

locations (saving tedious calculations and manually updating addresses when a program is

slightly modified), and macro facilities for performing textual substitution typically used to

encode common short sequences of instructions to run inline instead of in a subroutine.

Assemblers are far simpler to write than compilers for high-level languages.


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OPERATING SYSTEMS:

To run any software we need operating system. Embedded systems do not require a

complete operating system, which may make the system bulky, but only the basic functionalitiesof the operating system in a real time environmentRTOS. Off-the-shelf operating systems for

these systems began to appear in the late 1970s, and today several dozen viable options are

available. Embedded operating systems are available in variety of flavors: Windows NT,

LINUX, Windows CE 3.0, PalmOS, QNX, ROMDOS, JBED, RT kernel, Tiny BIOS, Turbo

task, Nucleus plus/Tasking, Diamond, and ThreadX etc. Out of these , a few major players have

emerged , such as Vxworks, PSOS, nucleus, windows CE, ThreadX and Linux. Inferno and

Chai are the two popular environments that are used to develop application stems

The Essence

An embedded system is a microcontroller-based, software driven, reliable, real-time control

system, autonomous, or human or network interactive, operating on diverse physical variables

and in diverse environments and sold into a competitive and cost conscious market.


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Embedded Systems Types:

High-end embedded & Lower- end embedded systems.

High-end embedded system - Generally 32,64 Bit Controllers used with OS.Examples: Personal Digital Assistant and Mobile phones etc .

Lower end embedded systems - Generally 8,16 Bit Controllers used with an minimaloperating systems and hardware layout designed for the specific purpose.

Examples: Small controllers and devices in our every day life like Washing Machine,

Microwave Owens , where they are embedded in.

Classification

Real Time Systems RTS classification

RTS is one which has to respond to events within a specified deadline

A right answer after the dead line is a wrong answer


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Hard Real Time Systems Soft Real Time System

"Hard" real-time systems have very narrow response time

Example: Nuclear power system , Cardiac pacemaker. "Soft" real-time systems have reduced constrains on "lateness" but still

must operate very quickly and repeatable.

Example: Railway reservation systemtakes a few extra seconds the

data remains valid.

CHARACTERISTICS

Designs are cost-sensitive Have real-time performance constraints Used withReal-Time Operating Systems (RTOS) Software failure can be life-threatening May have constraints on power consumption Operate over a wide-range of environmental conditions Fewer system resources then a desktop system All code might be stored in ROM Require specialized design tools May have on-chip debugging resources

Development Environment:

Development processor The processor on which we write and debug our programs Usually a PC. Target processor The processor that the program will run on in our embedded system often

different from the development processor.

Two embedded solutions uClinux and ELKS of Linux is focused on MMU-lessprocessors.


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