Delph1
Master of Science
Joined: 11 Dec 2003
Posts: 4750
Location: Pennybridge, Sweden
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 Posted: Sun Nov 20, 2005 2:44 pm Post subject: Latencies explained |
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I thought I would post some of the information that was available in the NordicHardware Encyclopedia we used to have:
| Quote: | Basically we have four types of latencies for memories: tRAS (Row Address Strobe), tRCD (RAS-to-CAS Delay), CAS (Column Address Strobe), tRP (RAS Precharge time). A good thing to know before is that the data stored in memories is built up like a matrix with rows and cells.
# tRCD is the amount of cycles it takes for the data on the memory to become available for reading/writing. Can be fractions (steps of ½) since DDR-ram can send in both ends of a cycle.
# CAS is the time it takes for the data to reach the output section of the memory.
# tRAS becomes valid when the memory has to read from different rows of the memory. tRAS is the amount of time it takes to switch row.
# tRP is the time needed to charge up the specific circuit. Affects tRAS.
Memory timings are in general sorted by importance: CAS - tRCD - tRP - tRAS. (e.g. 2-3-3-6) |
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