Memory Instruction
We need some more instruction to work with the computer. Apart from the instruction needed to perform task inside CPU, we need some more instructions for data transfer from main memory to CPU and vice versa.
In our hypothetical machine, we use three signal lines to identify a particular instruction. If we want to include more instruction, we need additional signal lines.
| Instruction |
Code |
Meaning |
| 1000 |
LDAI imm
|
Load register A with data that is given in the program
|
1001 |
LDAA addr
|
Load register A with data from memory location addr
|
| 1010 |
LDBI imm
|
Load register B with data
|
1011 |
LDBA addr
|
Load register B with data from memory location addr
|
1100 |
STC addr
|
Store the value of register C in memory location addr
|
1101 |
HALT
|
Stop the execution
|
1110 |
NOP
|
No operation
|
1111 |
NOP
|
No operation
|
With this additional signal line, we can go upto 16 instructions. When the signal of this new line is 0, it will indicate the ALU operation. For signal value equal to 1, it will indicate 8 new instructions. So, we can design 8 new memory access instructions.
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