A Comparative Analysis of Conventional 8051 Microcontroller with Modern Ultra

Low Power MSP430 #1Nishit Chittora, #2Akshay Nigam, #3Pankaj Chaudhary, #4Saurabh Porwal

nish2405@gmail.com, pankajchaudhary1708@gmail.com, akshaynigam89@yahoo.in,

porwalnk@rediffmail.com 1, 2, 3 Electronics & Communication Engineering Department,

4Sr. Lecturer, Electronics & Communication Engineering Department, #Geetanjali Institute of Technical Studies, Udaipur

Abstract— Computational tools and computing machines were always the attraction and motivation for the technological implementation in the field of industrial and domestic products. The popularity of microcontroller is ever increasing, as fuelled by the advances in the semiconductor industry. They are embedded in almost any device connected to power or battery. The limitations of digital electronics have almost vanished today, due to emergence of these varieties of powerful microcontrollers. By reducing the size and cost compared to a design that uses a separate microprocessor, memory, and input/output devices, microcontrollers make it economical to digitally control even more devices and processes consuming less power. In this paper featural characteristic of latest processor MSP430 is highlighted. These processors utilize common, integrating analog components to control non-digital electronic systems. A comparison is done among different features of the ultra low power MSP430 with the conventional 8051 microcontroller. Broad application areas and advantages of MSP430 microcontroller over 8051 are also illustrated and reviewed in terms of power consumption and additional on-chip components. Keywords—Microcontroller, 8051, MSP430, Architectural features, low-power modes.

I. INTRODUCTION

A microcontroller is a functional computer system-on-a-chip. It contains a processor core, memory and programmable input/output peripherals. They consume relatively little power (milliwatts), and will generally have the ability to retain functionality while waiting for an event such as button press or interrupt. As they are programmable, its programs must fit in the available on-chip program memory to reduce its cost. Since processors interpret and process digital data, i.e. only 1s and 0s only, they won’t be able to do anything with the analog signals that may be being sent to it by a device. So as an A/D converter is used to convert the incoming data into a form that the processor can recognise. Microcontrollers are now used in all automatically controlled products and devices, such as automobile engine control systems, implantable medical devices, remote controls,

office machines, appliances, power tools, and toys.

The first industry efficient microcontroller Intel MCS-51 is based on Harvard architecture. It is single chip microcontroller (µC) series which was developed by Intel in 1980 for use in embedded systems. Intel's original versions were popular in the 1980s and early 1990s, but has today largely been superseded by a vast range of faster and/or functionally enhanced 8051-compatible devices manufactured by more than 20 independent manufacturers. Intel's original MCS-51 family was developed using NMOS technology, but later versions, identified by a letter C in their name (e.g., 80C51) used CMOS technology and were less power-hungry than their NMOS predecessors. This made them more suitable for battery-powered devices. However, as the need has grown, a desire to control more number of hip components has increased, which seeks more power.

Fig. 1 Basic block diagram of microcontroller

The Texas Instrument’s MSP430 is a mixed-

signal microcontroller family from Texas Instruments. Built around a 16-bit CPU, the MSP430 is designed for low cost, and specifically, low power consumption embedded applications. The MSP430 is particularly well suited for metering, wireless radio frequency engineering (RF), or battery-powered applications.

In MSP430 a 16-bit RISC CPU, peripherals and flexible clock system are combined by using a Von-Neumann common memory address bus (MAB) and memory data bus (MDB). Partnering a modern CPU with modular memory-mapped analog and digital peripherals, the MSP430 offers solutions for all mixed-signal applications.

Fig. 2 Block diagram of MSP430 microcontroller

II. POWER MANAGEMENT

Power management would be much simpler if all portable electronics requires the same operating voltage. In recent years, power consumption has moved to the forefront of digital IC development concerns. The combination of higher clock speeds, greater functional integration, and smaller process geometries has contributed to significant growth in power density. Furthermore, with every new process generation, leakage power consumption increases at an exponential rate.

Most parts have a shutdown or sleep mode available that will reduce the current consumption of the component considerably. In general, digital parts consume significant current when their transistors switch because of the charging and discharging of the internal capacitances of the transistors. Analogue integrated circuits also support shutdown modes to reduce power consumption. It is important to note that when a device is in shutdown mode, power and ground voltages are still powered and connected to the device.

In order to shutdown most integrated circuits, all that is required is a shutdown or sleep pin to be asserted properly. Other devices require a shutdown command to be issued over the bus. The primary disadvantages of shutdown modes, apart from the fact that the device is inoperative is that recovering back into normal operating modes can impose a significant delay.

In battery operated electronic devices, the energy required to execute given tasks set is one of very important parameters. The modern MSP430 microcontroller provides a number of methods to reduce microcontroller power requirements by selecting among the various available low power modes. In lower power

mode, the processor can achieve current in the microamps while still monitoring its inputs. The modes vary the degree to which the processor is aware of its surroundings and the clocks that the processor keeps running. Further a useful property of the MSP430 is that its recovery time from some low-power modes is fast enough to meet the response times of interrupts.

III. CHARACTERISTIC FEATURES

A. 8051 Microcontroller Key Features

The 8051 architecture provides many functions (CPU, RAM, ROM, I/O, interrupt logic, timer, etc.) in a single package 1. 8-bit ALU, Accumulator and 8-bit Registers,

hence it is an 8-bit microcontroller. 2. 8-bit data bus – It can access 8 bits of data in

one operation 3. 16-bit address bus – It can access 216 memory

locations – 64 KB (65536 locations) each of RAM and ROM

4. On-chip RAM – 128 bytes (data memory) 5. On-chip ROM – 4 KByte (program memory) 6. Four byte bi-directional input/output port 7. UART (serial port) 8. Two 16-bit Counter/timers 9. Two-level interrupt priority 10. Two power saving modes

B. MSP430 Microcontroller Key Features

MSP430 offers 200+ ultra-low power microcontrollers devices. Each device features a flexible clocking system. MSP430 ensures that the application only uses the appropriate clocks and peripherals that are needed to perform the task at hand. Several features make the MSP430 suitable for low-power and portable applications, which are hardly present in 8051 microcontroller: 1. MSP430 has low power consumption,

a. It takes only 0.1µA for RAM data retention.

b. Requires 0.8 µA for real time clock mode operation.

c. And 250 µA per MIPS (Machine Instructions per Second) at active operation

2. It works on low operating voltages ranging from 1.8 V to 3.6 V in different operating modes.

3. The port has low leakage current typically less than 50nA.

4. These controllers can be put easily from active mode to low-power mode by controlling bits in the status register. These supports several low-power modes, depending on how much of the device should remain active and how quickly it should return to full-speed operation.

5. MSP430 contain specialized on-chip analogue components for various types of measurement like a. 10/12/16-bit Analog-to-Digital

Converter (ADC)

b. 12-bit dual Digital-to-Analog Converter (DAC)

c. Comparator-gated timers to count for events.

d. Operational Amplifiers for comparison. e. Supply Voltage Supervisor (SVS) to

generate a system reset (POR) when the external supply voltage drops below a user-selectable threshold.

6. These controllers can drive directly many portable devices such as USART, I2C/SPI Universal Serial Interface and LCD displays.

7. The architecture of these devices is 16-bit RISC (Reduced Instruction Set Computing) with following features: a. Instructions processing done on any bits,

bytes or words. b. Compact core design which reduces

power consumption and cost. c. Has 51 instructions (27 core + 24

emulated). d. Supports 7 addressing modes. e. Has extensive vectored-interrupt

capability. Any interrupt can wake up the MSP430 from low-power mode to active mode and transfer the routine of the program to vector locations causing that interrupt.

8. Availability of wide choice of clocks with different sources.

IV. REAL-TIME CAPABILITY WITH ULTRA-LOW

POWER CONSUMPTION

The design of the MSP430 was driven by the need to provide full real-time capability while still exhibiting extremely low power consumption. Average power consumption is reduced to the minimum by running the CPU and certain other functions of the MSP430 only when it is necessary. The rest of the time (the majority of the time), power is conserved by keeping only selected low-power peripheral functions active. But to have a true real-time capability, the device must be able to shift from a low-power mode with the CPU off to a fully active mode with the CPU and all other device functions operating nominally in a very short time. This was accomplished primarily with the design of the system clocks.

The MSP430 has three separate clocks that can run as quickly as 16 MHz in particular conditions. The reason three clocks instead of just one or even two is to compromise between systems that need speed and the ability to minimize power consumption, one of the real hallmarks of the MSP430. Faster clocks consume more power, so to really reduce the power used we need slower clocks. But some functions need to respond and conclude quickly, so we also need fast clocks. We can design around the use of a single clock, but having the flexibility of three is powerful. The three clocks available in BCS+ module are

A. MCLK: This is the Master Clock, the one that drives the processor and times the commands in your program. This is typically a high frequency clock, but can be configured for low frequencies if needed.

B. SMCLK: The Sub-Main Clock is a secondary clock that is often used by other peripherals. It can be the same frequency as MCLK or different, depending on the application.

C. ACLK: The Auxiliary Clock is usually timed outside the MSP430 and is typically used for peripherals. Often, this is a low frequency clock, but can also be used at high frequencies when desired.

All of the techniques that improve code efficiency will improve power efficiency. Increasing clock speed will not yield similar power savings because faster execution increases power consumption. Similarly, unused peripheral modules on the processor should be de-activated to save power.

V. MSP430 APPLICATION OPERATING MODES

MSP430 has six operating modes including the active mode, each with different power requirements. Three of these modes are important for battery-powered applications:

A. Active mode

In this mode the CPU and other device functions run all the time. It is used for calculations, decision-making, I/O functions, and other activities that require the capabilities of an operating CPU. All of the peripheral functions may be used, provided that they are enabled.

B. Low power mode 3 (LPM3)

This is the normal mode for most applications during 99% to 99.9% of the time. This mode is also called done mode or sleep mode. This mode is most important for battery-powered applications. The CPU is disabled, but enabled peripherals stay active. The basic timer provides a precise time base. When enabled, interrupts restore the CPU, switch on MCLK, and start normal operation.

C. Low power mode 4 (LPM4)

This mode is typically used during storage. This mode is also called off mode. It is used if the absolute lowest supply current is necessary or if no timing is needed or desired (no change of the RAM content is allowed). This is normally the case for storage preceding or following the calibration process.

VI. APPLICATIONS

Within the MSP430 platform, it includes 5 generations of ultra-low power, highly integrated microcontrollers spanning over 200 devices. It also offers various levels of analog integration, digital peripherals, and communication protocols

to help developers find the right microcontroller for various applications. MSP430 applications fall into two main classes, depending on the power supply:

For AC power-driven applications such as electricity meters and AC-powered controllers the microcontroller needs to be active at all times. The low current consumption of the MSP430 when active (900 µA @ 5V & fC = 1 MHz) puts it well within the typical low-power category now which is currently < 40 mA.

For battery-powered applications such as gas meters, water flow meters, heat volume counters, data loggers, and other controller and remote metering tasks power consumption is the key issue since operation from a single battery for 10 years or longer is often required. The average current drawn by the MSP430 needs to be in the range of the self discharge current of the battery, approximately 1 µA to 3 µA.

Thus the major applications of MSP430 are in Utility Metering, Portable Medical and instrumentation, Low-power Wireless Application, Intelligent Sensing, Communication and telecom, Consumer Electronics, Security Systems, Energy and lightening, Space Avionics and Defence, Transportation Automotive.

The conventional 8051 microcontrollers are generally used in Home Appliances, Office Accessories, Portable electronic gadgets, biomedical instrumentation, Automobile industries, mission critical application, solar panels etc.

VII. CONCLUSION

One of the most important quality standards for battery powered devices is battery life. Handheld medical tools, electricity meters, personal digital assistants, and a goal of the designer and programmer is to lower the power use of the embedded system to negligible levels. In designing battery powered devices, savings can be gained from the choice of electronic components, the arrangement of components, and the software on the design. The MSP430 supports various low power modes thus we can conclude that, the ultra-low power mixed-signal microcontrollers from TI provides the ultimate solution for a wide range of low power and portable applications.

To enable the adoption of advanced low-power techniques by mainstream users, the MSP430 fulfils the need for a design flow which holistically addresses the architecture, design, verification, and implementation of low-power designs.

The major advantage of MSP430 is that it requires very low input power supply for its operation, Further more it has inbuilt ADC and DAC which are not present in 8051 microcontroller. The MSP430's DMA allows data transfers from one address to another without CPU intervention, across the entire address range. This features up to three independent transfer channels.

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Design, 2011, First Edition, Ashirwad Publications, ISBN: 9789380343433.

[2] John H. Davies, MSP 430 Microcontroller Basics, 2010, Elsevier Inc., ISBN: 9780750682763

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[4] MSP430 Microcontroller Essentials, CD-ROM from Texas Instruments, 2009.

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[8] Satish Shah, 8051 Microcontrollers: MCS51 family and its variants, 2010, First Edition, Oxford University Press, ISBN:9780198063575

[9] I. Scott Mackenzie and Raphael C.-W. Phan, The 8051 Microcontroller, 2008, Fourth Edition, Pearson Education, ISBN: 9788131720189

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[11] http://en.wikipedia.org/wiki/Intel_MCS-51 [12] http://en.wikipedia.org/wiki/TI_MSP430 [13] http://focus.ti.com/mcu/docs/mcumspoverview.tsp?sect

ionId=95&tabId=140&familyId=342

TABLE 1 COMPARISON BETWEEN 8051 AND MSP430

Features 8051 MSP430 CPU width 8-bit 16-bit Architecture

8-bit internal data bus width and 16-bit internal address bus with Harvard architecture

Flexibility of 16 data and address fully-addressable, single-cycle 16-bit CPU registers

Register Sets 8-bit and 16-bit 16-bit CPU registers Type of processor CISC RISC Addressing modes 5 7 Clocking System Fixed Flexible Clocking System with MCLK, ACLK

and SMCLK Interfacing General purpose Devices

interfaced externally A wide selection of on-chip general purpose devices based on specific MSP430Fxxx platform.

Instruction sets 255 instructions 51 instructions (27 core + 24 emulated) Timers 2 to 3 Several timers few of which have capture compare

modes Watch Dog No Yes Power requirement 5 Volt 1.8-3.6 Volt Power dissipation 1.5Watt 4.5mW On-chip components Not Available Available on-chip – USB, LCD, LCD_A

controllers, Software RTC Module ADC and DAC External interface required Available on-chip

10, 12 and 16-bit different ADCs in specific devices

On-chip wireless features

Not Available Available

DMA Not Available Available upto 3 to 8 channels Low power modes Two mode available Five modes available Programming Interface Aging RS232 4-wire JTAG and Spy Bi-wire interface Cost Comparatively high Low-cost, lower-end applications.

Ideal for high-volume/Low-cost designs (25 cents)

AUTHORS

Saurabh Porwal is a Sr. Lecturer in the department of Electronics & Communication Engineering Geetanjali Institute of Technical Studies, Udaipur. He has a professional

experience of working with Microcontrollers, Automation & Instrumentation parts. He has guided several projects based on Embedded System design starting from hardware designing to complete logic development, one of which got sponsored from Department of Science and Technology, Rajasthan. He has contributed and presented several papers in various reputed International & National Conferences & Seminars of IEEE, IETE & IEI. He has acted as co-editor in the Book of Proceedings of the IEEE National Conference NCACA-2009 and also authored a text book on Embedded System Design for students of undergraduate level.

Nishit Chittora is pursuing his technical graduation in Electronics and Communication Engineering at Geetanjali Institute of Technical Studies, Udaipur. He has undergone training in HMT Machines Tools Ltd.,

Ajmer, on programmable Logic Controller. His subjects of interest are Microcontroller, Microprocessor, Control System, Robotics and Digital Electronics. He is currently working on the project Ultrasonic Range Finder based on microcontroller 8051.

Akshay Nigam is pursuing his technical graduation in Electronics and Communication Engineering at Geetanjali Institute of Technical Studies, Udaipur. He has undertaken training on PLC

& DCS systems in Videocon Industries Limited. He has also attended IEEE International Workshop on RF and Microwave. His subjects of interest are Microcontroller, Wireless Communication and Digital Signal Processing. Currently he is working on DTMF based Telephone Remote Control and Automation.

Pankaj Chaudhary is pursuing his technical graduation in Electronics and Communication Engineering at Geetanjali Institute of Technical Studies, Udaipur. Apart from this he has also designed and developed

website of department of Electronics & Communication Engineering, GITS. His subjects of interest are Microcontroller, Microprocessor & Digital Electronics. He is currently working on the project Ultrasonic Range Finder based on microcontroller 8051.

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