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An address bus is a bus that is used to specify a physical address. When a processor or DMA-enabled device needs to read or write to a memory location, it specifies that memory location on the address bus (the value to be read or written is sent on the data bus). The width of the address bus determines the amount of memory a system can address.
A system bus is a single computer bus that connects the major components of a computer system, combining the functions of a data bus to carry information, an address bus to determine where it should be sent or read from, and a control bus to determine its operation. The technique was developed to reduce costs and improve modularity, and ...
Diagram of relationship between the virtual and physical address spaces. In computing, a physical address (also real address, or binary address), is a memory address that is represented in the form of a binary number on the address bus circuitry in order to enable the data bus to access a particular storage cell of main memory, or a register of memory-mapped I/O device.
Bus (computing), a communication system that transfers data between different components in a computer or between different computers Memory bus, a bus between the computer and the memory; PCI bus, a bus between motherboard and peripherals that uses the Peripheral Component Interconnect standard
Address modifiers specify the number of significant address bits, the privilege mode (to allow processors to distinguish between bus accesses by user-level or system-level software), and whether or not the transfer is a block transfer. Below is an incomplete table of address modifiers:
Ranks are sub-units of a memory module that share the same address and data buses and are selected by chip select (CS) in low-level addressing. For example, a memory module with 8 chips on each side, with each chip having an 8-bit-wide data bus, would have one rank for each side for a total of 2 ranks, if we define a rank to be 64 bits wide.
large bus-widths (64/128/256/512/1024 bit). A simple transaction on the AHB consists of an address phase and a subsequent data phase (without wait states: only two bus-cycles). Access to the target device is controlled through a MUX (non-tristate), thereby admitting bus-access to one bus-master at a time.
An initiator has also to provide the data related to the specified address(es) on the Write data channel: the data on WDATA; the "strobe" bits on WSTRB (if present), which conditionally mark the individual WDATA bytes as "valid" or "invalid" Like in the read path, on the last data word, WLAST has to be asserted by the initiator.