A memory buffer register (MBR) or memory data register (MDR) is the
register
Register or registration may refer to:
Arts entertainment, and media Music
* Register (music), the relative "height" or range of a note, melody, part, instrument, etc.
* ''Register'', a 2017 album by Travis Miller
* Registration (organ), th ...
in a computer's
CPU that stores the data being transferred to and from the immediate access storage. It contains a copy of the value in the memory location specified by the
memory address register
In a computer, the memory address register (MAR) is the Central processing unit, CPU Hardware register, register that either stores the memory address from which data will be fetched to the CPU registers, or the address to which data will be sent ...
. It acts as a
buffer
Buffer may refer to:
Science
* Buffer gas, an inert or nonflammable gas
* Buffer solution, a solution used to prevent changes in pH
* Buffering agent, the weak acid or base in a buffer solution
* Lysis buffer, in cell biology
* Metal ion buffer
* ...
, allowing the processor and
memory units to act independently without being affected by minor differences in operation. A data item will be copied to the MBR ready for use at the next
clock
A clock or a timepiece is a device used to measure and indicate time. The clock is one of the oldest human inventions, meeting the need to measure intervals of time shorter than the natural units such as the day, the lunar month and the ...
cycle, when it can be either used by the processor for reading or writing, or stored in main memory after being written.
This register holds the contents of the memory which are to be transferred from memory to other components or vice versa. A
word
A word is a basic element of language that carries an semantics, objective or pragmatics, practical semantics, meaning, can be used on its own, and is uninterruptible. Despite the fact that language speakers often have an intuitive grasp of w ...
to be stored must be transferred to the MBR, from where it goes to the specific memory location, and the arithmetic data to be processed in the
ALU first goes to MBR and then to accumulated register, and then it is processed in the ALU.
The MDR is a ''two-way register.'' When data is fetched from memory and placed into the MDR, it is written to go in one direction. When there is a write instruction, the data to be written is placed into the MDR from another CPU register, which then puts the data into memory.
The memory data register is half of a minimal interface between a
microprogram
In processor design, microcode (μcode) is a technique that interposes a layer of computer organization between the central processing unit (CPU) hardware and the programmer-visible instruction set architecture of a computer. Microcode is a lay ...
and
computer storage
Computer data storage is a technology consisting of computer components and recording media that are used to retain digital data. It is a core function and fundamental component of computers.
The central processing unit (CPU) of a compute ...
; the other half is a
memory address register
In a computer, the memory address register (MAR) is the Central processing unit, CPU Hardware register, register that either stores the memory address from which data will be fetched to the CPU registers, or the address to which data will be sent ...
(MAR).
Digital registers
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