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Why is the wait for memory function completed step needed when reading from or writing to main memory?
Wiki User
∙ 12y ago
When CPU needs to access a memory location for read or write, it places an address on the address bus. In case of Read, data is meant to be read into Memory Data Register (MDR) and in case of Write, the data (to be written to memory) is put in the MDR.
After that CPU issues the Read or Write signal.
However, CPU needs to know when the desired memory function (Read or Write) has been completed..
This line back to the CPU saying that the operation is complete is sometimes called memory function complete (MFC).
In the meanwhile, the instruction or step that is executed by the CPU is known as Wait for Memory Function Completed (WMFC)
To summarize:
- To read (if you are a CPU):
- Put the desired memory address in the MAR.
- Assert the Read control line.
- Wait for the MFC line to be set to 1 by the main memory unit.
(Or wait for the appropriate amount of time, if there's no MFC line with your particular main memory unit you are using (rare these days).)
- Get the data out of the MDR.
- To write (again, if you are a CPU):
- Put the desired memory address in the MAR and put the desired data in the MDR.
- Assert the Write control line.
- Wait for the MFC line to be set to 1 by the main memory unit
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∙ 12y ago
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What is the process of transferring data instructions and information from a storage medium into memory?
reading
Why Is Wait For Memory Function Completed Step Needed When Reading From Or Writing To The Main Memory?
When CPU needs to access a memory location for read or write, it places an address on the address bus. In case of Read, data is meant to be read into Memory Data Register (MDR) and in case of Write, the data (to be written to memory) is put in the MDR.After that CPU issues the Read or Write signal.However, CPU needs to know when the desired memory function (Read or Write) has been completed..This line back to the CPU saying that the operation is complete is sometimes called memory function complete (MFC).In the meanwhile, the instruction or step that is executed by the CPU is known as Wait for Memory Function Completed (WMFC)To summarize:To read (if you are a CPU): Put the desired memory address in the MAR.Assert the Read control line.Wait for the MFC line to be set to 1 by the main memory unit. (Or wait for the appropriate amount of time, if there's no MFC line with your particular main memory unit you are using (rare these days).)Get the data out of the MDR.To write (again, if you are a CPU): Put the desired memory address in the MAR and put the desired data in the MDR.Assert the Write control line.Wait for the MFC line to be set to 1 by the main memory unit
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