Search results
Results from the WOW.Com Content Network
RAS only refresh – In this mode the address of the row to refresh is provided by the address bus lines typically generated by external counters in the memory controller. CAS before RAS refresh (CBR) – In this mode the on-chip counter keeps track of the row to be refreshed and the external circuit merely initiates the refresh cycles. [5]
The refresh cycles are distributed across the entire refresh interval in such a way that all rows are refreshed within the required interval. To refresh one row of the memory array using RAS only refresh (ROR), the following steps must occur: The row address of the row to be refreshed must be applied at the address input pins.
This is like power down, but the SDRAM uses an on-chip timer to generate internal refresh cycles as necessary. The clock may be stopped during this time. While self-refresh mode consumes slightly more power than power-down mode, it allows the memory controller to be disabled entirely, which commonly more than makes up the difference.
Refresh commands are also different from a conventional SDRAM. There is no "refresh all banks" command, and the refresh operation is divided into separate activate and precharge operations so the timing is determined by the memory controller. The refresh counter is also programmable by the controller. Operations are:
A memory controller, also known as memory chip controller (MCC) or a memory controller unit (MCU), is a digital circuit that manages the flow of data going to and from a computer's main memory. [ 1 ] [ 2 ] When a memory controller is integrated into another chip, such as an integral part of a microprocessor , it is usually called an integrated ...
This is the number of cycles it takes to read the first bit of memory from a DRAM with the correct row already open. Unlike the other numbers, this is not a minimum, but an exact number that must be agreed on between the memory controller and the memory. Row Address to Column Address Delay T RCD
One advantage of keeping the clock frequency low is that it reduces the signal integrity requirements on the circuit board connecting the memory to the controller. The name "double data rate" refers to the fact that a DDR SDRAM with a certain clock frequency achieves nearly twice the bandwidth of a SDR SDRAM running at the same clock frequency ...
Dynamic RAM is more complicated for interfacing and control, needing regular refresh cycles to prevent losing its contents, but uses only one transistor and one capacitor per bit, allowing it to reach much higher densities and much cheaper per-bit costs. [2] [23] [37]