Basic Memory Operations
The memory unit supports two basic operations: read and write. The read operation reads previously stored data and the write operation stores a new value in memory. Both of these operations require a memory address. In addition, the write operation requires specification of the data to be written. The address and data of the memory unit are connected to the address and data buses of the system bus, respectively. The read and write signals come from the control bus. Two metrics are used to characterize memory. Access time refers to the amount of time required by the memory to retrieve the data at the addressed location. The other metric is the memory cycle time, which refers to the minimum time between successive memory operations.
The read operation is nondestructive in the sense that one can read a location of the memory as many times as one wishes without destroying the contents of that location. The write operation, however, is destructive, as writing a value into a location destroys the old contents of that memory location.
Steps in a Typical Read Cycle:
1. Place the address of the location to be read on the address bus,
2. Activate the memory read control signal on the control bus,
3. Wait for the memory to retrieve the data from the addressed memory location and place them on the data bus,
4. Read the data from the data bus,
5. Drop the memory read control signal to terminate the read cycle.
المادة المعروضة اعلاه هي مدخل الى المحاضرة المرفوعة بواسطة استاذ(ة) المادة . وقد تبدو لك غير متكاملة . حيث يضع استاذ المادة في بعض الاحيان فقط الجزء الاول من المحاضرة من اجل الاطلاع على ما ستقوم بتحميله لاحقا . في نظام التعليم الالكتروني نوفر هذه الخدمة لكي نبقيك على اطلاع حول محتوى الملف الذي ستقوم بتحميله .
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