digital logic - What is the difference between PLA and ROM?

I'm finding it hard to understand. What is the difference between PLA and ROM? Can somebody please provide a link or explanation?

Answer

They are quite different devices.

PLA = Programmable Logic Array.

A PLA or PAL (programmable array logic) device is like a baby FPGA which can be programmed to perform basic logic functions. Tens to hundreds of gates on a PAL can be connected to perform simple logic functions. A PAL is often read only, in that after programming you have to perform a complete erase to update it.

ROM = Read Only Memory.

A ROM does not perform logic functions, but stores data. A type of ROM might be EPROM, eraseable programmable read only memory.

You can use a ROM as a logic device, by implementing a simple logic table lookup. Like a truth table. However, it is somewhat wasteful and expensive to do this compared to actually using a PAL or even a CPLD/FPGA.