Page 151 - DCAP108_DIGITAL_CIRCUITS_AND_LOGIC_DESIGNS

Digital Circuits and Logic Design

Notes 9. .............. is the set of instructions.
(a) Micro-process (b) Micro-processor
(c) Multi-program (d) Micro-program

8.9 Summary

• CPU contains necessary circuitry for data processing controlling other components of the
computer.
• Every computer has such a storage space known as primary storage, main memory, or
simply memory.
• A manufacturer programmed ROM is one in which data is burnt in by the manufacturer
of the electronic equipment in which it is used.

• Selective programming be done to an EEPROM chip. The user can alter the value of certain
cells without needing to erase the programming on other cells.

• Data stored in an EEPROM chip is permanent, at least until the user decides to erase and
replace the information it contains.

• While the EEPROM can be reprogrammed, the number of times it can be altered is limited.

8.10 Keywords

EPROM chips: these are of two types - one in which the stored information is erased by exposing
the chip for some time of ultraviolet light and the other one in which the stored information is
erased by using high voltage electric pulses is known as Ultra Violet EPROM ((UVEPROAM)
and the latter is known as Electrically EPROM (EEPROM).

Erasable programmable read-only memory (EPROM): It overcomes this problem as the name
implies, it is possible to erase information stored in an EPROM chip and the chip can be
reprogrammed to store new information.
Programmable logic array (PLA): It is a large scale integrated programmable logic device which
is used for synthesizing combinational logic functions.

Read-only memory (ROM): It is a non-volatile memory chip in which data is stored permanently
and cannot be altered by usual programs. In fact, storing data permanently into this kind of
memory is called “burning in the data” because data in such memory is stored by using fuse-links.
Tunneling: The electrons of the floating gate towards the oxide layer separating the floating gate
and the control gate is still the method of changing a bit’s value from 1 to 0.

1. Draw the logic circuit and truth table of Programmable Logic Array.

2. Prepare a truth table of vertical wires with three inputs.

8.11 Review Questions

1. Define the RAM and draw the block diagram of RAM.
2. Explain the difference between RAM and ROM.

3. What is a sequential-access storage device?
4. Distinguish between a sequential access, a direct access, and a random access storage device.
Write one example of each.

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