Multiple choiceQuestion 1 · Recall
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By the end you can explain the differences between PROM, EPROM and EEPROM: how each is written, how (or whether) it can be erased, and where each is used.
You've built a robot and put its control program on a ROM chip. Then you spot a bug.
What happens next depends on the chip:
Plain ROM (sometimes called mask ROM) has its contents built in during manufacture. Nobody can ever change them.
The other three are all non-volatile, like ROM. Each one adds a bit more freedom to write: Programmable, then Erasable, then Electrically Erasable.
PROM (programmable ROM)
ROM that is made blank and can be programmed once after manufacture, by using a high voltage to blow fuses in the chip. After that, its contents cannot be erased or changed.
EPROM (erasable PROM)
PROM that can be erased by strong ultraviolet (UV) light shone through a quartz window on the chip, then reprogrammed. The chip must be removed from the circuit, and the whole chip is erased at once.
EEPROM (electrically erasable PROM)
PROM that can be erased and rewritten using an electrical signal (voltage) while it is still in the circuit. Data can be rewritten byte by byte.
Worked example: Easy first: fixing the robot's bug
The robot's control program has a bug. Describe how the fix is put onto each type of chip.