INTERCHIP SERIAL COMMUNICATIONS

Serial data links are not always restricted to long-distance communications. Within a single computer system, or even a single circuit board, serial links can provide attractive benefits as compared to traditional parallel buses. Computer architectures often include a variety of microprocessor peripheral devices with differing bandwidth requirements. Main memory, both RAM and ROM, is a central part of computer architecture and is a relatively high-bandwidth element. The fact that theCPU must continually access main memory requires a simple, high-bandwidth interface—a parallel bus directly or indirectly driven by the CPU. Other devices may not be accessed as often as main memory and therefore have a substantially lower bandwidth requirement. Peripherals such as data acquisition ICs (e.g., temperature sensors), serial number EEPROMs, or liquid crystal display (LCD) controllers might be accessed only several times each second instead of millions of times per second. These peripherals can be directly mapped into the CPU’s address space and occupy a spot on its parallel bus, but as the number of these low-bandwidth peripherals increases, the complexity of attaching so many devices increases.