Page 181 - Bebop to The Boolean Boogie An Unconventional Guide to Electronics Fundamentals, Components, and Processes

Memory ICs

Memory devices are a special class of integrated circuits that are used to
store binary data for later use. There are two main categories of semi-conductor
memories: read-only memory (ROM) and read-write memory (RWM) . Other
components in the system can read (extract) data from ROM devices, but
cannot write (insert) new data into them. By comparison, data can be read out
of RWM devices and, if required, new data can be written back into them. The
act of reading data out of a RWM does not affect the master copy of the data
stored in the device. For a number of reasons, mainly historical, RWMs are
more commonly known as random-access memories (RAMS).
ROM and RAM devices find a large number of diverse applications in
electronic designs, but their predominant usage is as memory in computer
systems (Figure 15 - 1 ) .

control-bus
address-bus
data-bus

Figure 15-1. ROM and RAM in a
computer system

In conversation, ROM is pronounced as a single word to rhyme with “bomb,” while “RAM” is
pronounced to rhyme with “ham.”