14-08-2012, 12:13 PM
SIC Machine
Basic info about SIC Machine.docx (Size: 92.99 KB / Downloads: 28)
Basic info about SIC Machine
SIC machine is a hypothetical computer that is designed to illustrate hardware features and concepts. It has two versions: the first is called the standard model (SIC) and the second is called the extended equipment version (SIC/XE). SIC/XE has extra features compared to the standard model; however, it is compatible with standard model.
User Guide
There are a couple of things you should know before starting using the SIC/XE Machine; like what is the ISA of the machine and how to use it and what resources you have to use it. We talked before basic info about the machine, but now we will talk in details how to use it.
Addressing modes & Flag Bits
There are five addressing mode in this machine as the following:
Direct Addressing: (x & b & p bits are all set to zero)
(n,i) bits are both set to the same value either 1 or 0, if they are both 00 then the format is basic SIC Machine (Format 1)
Relative Addressing: (PC Relative addressing or Base Relative addressing) It depends on the (b,p) bits, if b=1 then then the address of the operand should be added the value of the base register, and ig p=1 the operand should be added the value of the PC register.
The difference between these Addressing modes is the following:
- Simple Addressing: to obtain the value needed for the instruction, we should calculate the target address depending on (nixbpe bits) and then go to that address take the value stored in the location pointing at and use it.
- Indirect Addressing: we first calculate the target address using (nixbpe bits) then we go to the location that address pointing at and pick up the value in it and use it as another address and also follow that one then the value stored in the second location is what we need for the instruction.
- Immediate Addressing: the value we need is the operand value itself.