And a main memory connected to the role of
It is in the running stored programs and data (or a portion) of the member, through the address bus and the CPU data control communication with the three other components.
A storage unit (word or byte) address bus for selecting a main memory, which determines the maximum number of bits of memory cells can be accessed. Called a maximum addressable space. For example, when addressed by byte, 20-bit address space may be accessed 1MB of memory, 32-bit address can access the storage space of 4GB.
A data bus for transferring data between the computer of the features, the product of the number of bits of the data bus (bus width) with the bus clock frequency, the highest supported data bus throughput (input / output) can be proportional.
A control bus for specifying the type of bus and the current duty cycle input / out completion timing. The duty cycle of the bus may include a main memory read cycle, a main memory write cycle, I / O read cycle devices, I / O device write cycle, i.e. with a different bus cycles of use to distinguish that component (main memory or I / O nature of the device) and the operation (read or write) as well as direct memory access (DMA) bus cycles.
Main memory read and write process
Read process:
address given
shows a chip select and write commands
to save the read contents
Write process:
given address
given chip select and data
given write command
Storage principle of dynamic memory
Dynamic memory is a metal oxide semiconductor (MOS) of the MOS transistor to store a single bit (bit) information. Information is stored in the source mos tube T of the parasitic capacitance Cs electrode, for example, Cs with stored charge represents a 1, 2 indicates uncharged.
Dynamic memory operating characteristics
- Destructive readout
forcibly cleared when read
precharge delay - Require periodic refresh
centralized refresh
stop reading and writing progressive refresh - Dispersed refresh
timing cycle refresh
quick paging organizations
Process dynamic memory reader
Highly integrated dynamic memory, large storage capacity, to save the number of pins, into row address and column selection is.
Dynamic memory storage principle
-
Writing
to the data bit lines transmitting
the selected word line -
Reading
the bit line is set high
is selected word line
sensing and amplifying capacitor discharge if
writeback -
Refresh
regular batch read operation
Dynamic characteristics of the reservoir
- The high capacity of the memory
unit memory cell area smaller - Access slow
capacitor charging and discharging
refresh - Low energy consumption
- Low Price
