Digital Electronics: Principles, Devices and Applications

Microprocessors 53913.6.1.5 Software supportThe associated software with the microprocessor, such as the debugger, compiler and operating system,constitutes one of the factors that needs to be considered.13.6.1.6 Code densityThe code density is the ratio between the size of the source code and the size of the object code.The smaller the object code, the better is the code density. Processors having high code densitiesrequire less memory to execute the code. RISC processors have poor code density compared withCISC processors.Moreover, there is seldom one right microprocessor for a given task. There are several chips thatcan be used for a given task. Factors such as past experience, the market reputation of the processorand availability are considered before making the final decision.13.6.2 Microprocessor Selection Table for Common ApplicationsSingle-chip microcomputers are commonly used in control applications. In more complex controlapplications requiring large amounts of I/O, memory or high-speed processing, eight-bit or 16-bitmicroprocessors are used. Data processing applications, which require more memory and I/O, use aPC. The 32-bit and 64-bit microprocessors are used in systems that require high performance such asengineering workstations and in multi-user systems. Table 13.2 gives typical microprocessor types forvarious application classes.Table 13.2Microprocessor types for various application classes.Application classesTypical device typesTypeSpeed andcomplexityType exampleSingle-chipmicrocomputerMicroprocessorfour-bit eight-bit 16-bit eight-bit 16-bit 32/64-bitControl Low Automatic thermostat ̌ ̌Medium Digital multimeter ̌ ̌High Engine control ̌ ̌ ̌ ̌Data Low Home computer ̌processingMedium Mid-range PC ̌ ̌High Engineeringworkstation,multiusercomputeř̌