Version 2 EE IIT, Kharagpur 1
Introduction to Real Time Embedded Systems Part I
Version 2 EE IIT, Kharagpur 2
Example, Definitions, Common Architecture Instructional Objectives
After going through this lesson the student would be able to • • • • • • Know what an embedded system is distinguish a Real Time Embedded System from other systems tell the difference between real and non-real time Learn more about a mobile phone Know the architecture Tell the major components of an Embedded system
Digital Electronics, Microprocessors
In the day-to-day life we come across a wide variety of consumer electronic products. We are habituated to use them easily and flawlessly to our advantage. Common examples are TV Remote Controllers, Mobile Phones, FAX machines, Xerox machines etc. However, we seldom ponder over the technology behind each of them. Each of these devices does have one or more programmable devices waiting to interact with the environment as effectively as possible. These are a class of “embedded systems” and they provide service in real time. i.e. we need not have to wait too long for the action. Let us see how an embedded system is characterized and how complex it could be? Take example of a mobile telephone: (Fig. 1.1)
Version 2 EE IIT, Kharagpur 3
Fig. 1.1 Mobile Phones
Version 2 EE IIT, Kharagpur 4
When we want to purchase any of them what do we look for? Let us see what are the choices available? Phone Price Phone 1 Rs 5000/Weight / Size 88.1 x 47.6 x 23.6 mm 116 g Screen TFT1 65k Color 96x32 screen Games Camera Yes 4 x Zoom Radio Ring tones Memory No Polyphonic
Phone 2 Rs 6000/-
89 x 49 x 24.8 mm 123 g
Phone 3 Rs 5000/-
133.7 x 69.7 x 20.2mm 137g
Stauntman2 & Monopoly3 included more downloadable J2ME TFT Games: 65k Stauntman Color and 176x220 Monopoly screen More downloadable Symbian and 176 x Java 208 download pixel games or backlit packaged on screen MMC cards with 4096 colors
Integrated Digital Camera 1 M Pixel
Polyphonic and MP3
3.4 MB user memory built in.
Besides the above tabulated facts about the mobile handset, being a student of technology you may also like to know the following Network type GSM2 or CDMA3 (Bandwidth), Battery: Type and ampere hour Talk-time per one charge, Standby time
Short for thin film transistor, a type of LCD flat-panel display screen, in which each pixel is controlled by from one to four transistors. The TFT technology provides better resolution of all the flat-panel techniques, but it is also the most expensive. TFT screens are sometimes called active-matrix LCDs.
short form of Global System for Mobile Communications, one of the leading digital cellular systems. GSM uses narrowband Time Division Multiple Access (TDMA), which allows eight simultaneous calls on the same radio frequency. GSM was first introduced in 1991. As of the end of 1997, GSM service was available in more than 100 countries and has become the de facto standard in Europe and Asia.
Short form of Code-Division Multiple Access, a digital cellular technology that uses spread-spectrum techniques. Unlike competing systems, such as GSM, that use TDMA, CDMA does not assign a specific frequency to each user. Instead, every channel uses the full available spectrum. Individual conversations are encoded with a pseudo-random digital sequence. CDMA is a military technology first used during World War II by the English allies to foil German attempts at jamming transmissions. The allies decided to transmit over several frequencies, instead of one, making it difficult for the Germans to pick up the complete signal.
Version 2 EE IIT, Kharagpur 5
From the above specifications it is clear that a mobile phone is a very complex device which houses a number of miniature gadgets functioning coherently on a single device. Moreover each of these embedded gadgets such as