What are the timing parameters for DDR SDRAM?
For better understanding, the timing diagram of a memory with timing parameters 3-3-3-10 (assumed) is presented in figure 4. To conclude the article, we can summarize the timing parameters as below: CAS Latency (CL) is the time it takes to read the first bit of memory from a DRAM with the correct row already open.
How to create a Hyperlynx DDRx memory controller timing model?
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What does the X mean in DDRX YYYY?
In DDRx-yyyy, “x” represents the technology generation (example: DDR2, DDR3, DDR) and “yyyy” represents the DDR clock rate or more appropriately the data rate. DDR (double data rate), as the name suggests, transfers two chunks of data per clock cycle and hence achieve twice the performance as compared to the memory without this feature.
Why is DDR memory rated twice the clock rate?
DDR (double data rate), as the name suggests, transfers two chunks of data per clock cycle and hence achieve twice the performance as compared to the memory without this feature. It is for this reason that DDR are rated with twice the clock rate at which they function, i.e., the data rate.
How long does it take to refresh a SDRAM?
But before a REFRESH can be applied, all banks of the SDRAM have to be Precharged and idle for a minimum time of tRP (min). Once a REFRESH command is issued, there has to be a delay of tRFC (min) before the next valid command is issued (except DES command).
What’s the difference between DRAM and DDR SDRAM?
It is the delay time between the moment a memory controller tells the memory module to access a particular memory column on a RAM memory module, and the moment the data from given array location is available on the module’s output pins. In DDR SDRAM it is specified in clock cycles, while in asynchronous DRAM it is specified in nanoseconds.
How to read the first bit of memory from a DRAM?
The time to read the first bit of memory from a DRAM without any active row is tRCD + CL. The time to read the first bit of memory from a DRAM with the wrong row open is tRP + tRCD + CL. The number of clock cycles required between an “Active” command and issuing the “Precharge” command is tRAS.