Memory controller and method determining empty/full status of a FIFO memory using gray code counters
US5426756A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Aug 11, 1992 |
| Grant date | Jun 20, 1995 |
| Priority date | — |
| Expiry date | Aug 11, 2012 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06F2205/102
- WIPO fieldBasic communication processes
- WIPO sectorElectrical engineering
Abstract
A controller for asynchronous configurable FIFO (first-in-first-out) memory includes, in addition to two binary counters for the read pointer and write pointer, two Gray code counters for determining whether the FIFO is full or empty by a comparison of the read pointer and write pointer values expressed in Gray code. The Gray code counters avoid the problem of asynchronicity of read and write signals. The Gray code counters determine if the FIFO is full or empty depending on whether the pointer values match (indicating empty) or differ in accordance with particular Gray code patterns (indicating full). The Gray code counters each have an extra bit which allows determination of the full or empty condition from a straightforward comparison of the read pointer and write pointer values, while the Gray code eliminates the problem of multiple bit transition providing an incorrect indication of the pointer location. The controller is implemented in logic circuitry which is configurable depending on the FIFO configuration and system configuration considerations.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.