On the IAS, describe in English the process that the CPU must undertake to read a value from memory and to write a value to memory in terms of what is put into the MAR, MBR, address bus, data bus, and control bus.

To read a value from memory, the CPU puts the address of the value it wants into the MAR. The CPU then asserts the Read control line to memory and places the address on the address bus. Memory places the contents of the memory location passed on the data bus. This data is then transferred to the MBR. To write a value to memory, the CPU puts the address of the value it wants to write into the MAR. The CPU also places the data it wants to write into the MBR. The CPU then asserts the Write control line to memory and places the address on the address bus and the data on the data bus. Memory transfers the data on the data bus into the corresponding memory location.

Address Contents

1. 08A  LOAD M(0FA) STOR M(0FB)
   
2. 08B  LOAD M(0FA) JUMP +M(08D)
   
3. 08C  LOAD –M(0FA)
   

         08D

         STOR M(0FB)

This program will store the absolute value of content at memory location 0FA into memory location 0FB.