Archive for Oktober 2014
1.
The PC contains 300, the address of the first
instruction. This instruction (the value 1940 in hexadecimal) is loaded into
the instruction register IR and the PC is incremented. Note that this process
involves the use of a memory address register (MAR) and a memory buffer
register (MBR). For simplicity, these intermediate registers are ignored.
2. The first 4 bits (first hexadecimal digit) in the IR
indicate that the AC is to be loaded. The remaining 12 bits (three hexadecimal
digits) specify the address (940) from which data are to be loaded.
3. The next instruction (5941) is fetched from location 301 and
the PC is incremented.
4. The old contents of the AC and the contents of location 941
are added and the result is stored in the AC.
5. The next instruction (2941) is fetched from location 302 and
the PC is incremented.
6. The contents of the AC are stored in location 941.
