![]() ![]() they are usually much slower than dedicated logic circuits,.However, there are several disadvantages: Also, PROMs (programmable ROMs), EPROMs ( ultraviolet-erasable PROMs) and EEPROMs (electrically erasable PROMs) are available that can be programmed using a standard PROM programmer without requiring specialised hardware or software. The advantage of using a ROM in this way is that any conceivable function of the m inputs can be made to appear at any of the n outputs, making this the most general-purpose combinatorial logic device available. The ROM therefore becomes equivalent to n separate logic circuits, each of which generates a chosen function of the m inputs. ![]() Theoretically, there are 2^m possible Boolean functions of these m signals, but the structure of the ROM allows just n of these functions to be produced at the output pins. ![]() Now imagine that the inputs are driven not by an m-bit address, but by m independent logic signals. When used as a memory, the ROM contains 2^m words of n bits each. Consider a ROM with m inputs (the address lines) and n outputs (the data lines). Before PLDs were invented, read-only memory (ROM) chips were used to create arbitrary combinatorial logic functions of a number of inputs. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |