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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 time to read the first bit of memory from a DRAM with the wrong row open is T RP + T RCD + CL. Row Active Time T RAS: The minimum number of clock cycles required between a row active command and issuing the precharge command. This is the time needed to internally refresh the row, and overlaps with T RCD. In SDRAM modules, it is simply T RCD ...
Circuit board design: [52] New power supplies (VDD/VDDQ at 1.2 V and wordline boost, known as VPP, at 2.5 V); VrefDQ must be supplied internal to the DRAM while VrefCA is supplied externally from the board; DQ pins terminate high using pseudo-open-drain I/O (this differs from the CA pins in DDR3 which are center-tapped to VTT). [52]
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 ...
SDRAM designed for battery-powered devices offers some additional power-saving options. One is temperature-dependent refresh; an on-chip temperature sensor reduces the refresh rate at lower temperatures, rather than always running it at the worst-case rate. Another is selective refresh, which limits self-refresh to a portion of the DRAM array.
A schematic drawing depicting the cross-section of the original one-transistor, one-capacitor NMOS DRAM cell. It was patented in 1968. The cryptanalytic machine code-named Aquarius used at Bletchley Park during World War II incorporated a hard-wired dynamic memory.
A second type, DRAM (dynamic RAM), is based on MOS capacitors. Charging and discharging a capacitor can store either a '1' or a '0' in the cell. However, since the charge in the capacitor slowly dissipates, it must be refreshed periodically. Due to this refresh process, DRAM consumes more power, but it can achieve higher storage densities.
The ZX8301 [1] [2] is an Uncommitted Logic Array (ULA) integrated circuit designed for the Sinclair QL microcomputer.Also known as the "Master Chip", it provides a Video Display Generator, the division of a 15 MHz crystal to provide the 7.5 MHz system clock, ZX8302 register address decoder, DRAM refresh and bus controller.