Page 1030 - The Mechatronics Handbook

FIGURE 35.8 Simulation of continuous and sampled signal: aliasing.

FIGURE 35.9 Elements of a computer.

often called a microcomputer. The reader should be aware that a single electronics package can contain
many “chips,” which are connected by fine wires within the package. The overall package is still called a
chip. Finally, if the A/D and D/A functions are provided in the same package, the computer is often called
a DSP. However, these functions can also be contained in something which is called a microcomputer.
DSPs are also computers which have a special instruction in the ALU called a multiply-accumulate (MAC)
instruction even if the A/D and D/A are not present. Digital signal processing algorithms often involve
MAC instructions and a computer, which can execute this instruction very effectively (in one instruction
cycle of the computer), and are often called DSPs. To further complicate the situation, electronic devices
called application specific integrated circuits (ASICs) exist. These devices can be custom made to perform
a specific operation (such as a PID algorithm). ASICs can contain a CPU or memory or peripheral functions
or even a MAC cell as part of its makeup. If the reader is thoroughly confused by this explanation, he
probably has the proper grasp of the situation. However, he should be aware that diagrams like the one
shown in Fig. 35.9 often accompany the electronic component so the internal capabilities can be determined.
Before leaving computers, one final point will be made. Memory in a computer can often be divided
between program space and data space, as shown in Fig. 35.10. This representation is meant to be pictorial

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