SAP-1 Components

What is the Simple As Possible (SAP)-1 computer?
The SAP-1 computer is a bus-organized computer that uses of the von Neumann architecture.

What does the Simple As Possible (SAP)-1 computer make use of?
The SAP-1 computer makes use of an 8-bit central bus and ten main components.

What is a diagram of the Simple As Possible (SAP)-1 computer?
A diagram of the SAP-1 computer is:
SAP-1 Computer Diagram

What are the ten components of the Simple As Possible (SAP)-1 computer?
The ten components of the SAP-1 computer are:

  1. Program Counter.
  2. Input and Memory Address Register (MAR).
  3. Random-Access Memory (RAM).
  4. Instruction Register.
  5. Controller-Sequencer.
  6. Accumulator.
  7. Adder-Subtractor.
  8. B-Register.
  9. Output Register.
  10. Binary Display.

What does the Program Counter (PC) do?
The PC stores and sends out the memory address of the next instruction to be fetched and executed.

What does the Memory Address Register (MAR) do?
The MAR stores the 4-bit address of data or an instruction which is placed in memory.

Where does the Memory Address Register (MAR) get the 4-bit address of data or an instruction when the Simple As Possible (SAP)-1 computer is running?
When the SAP-1 computer is running, the MAR gets the 4-bit address of data or an instruction from the Program Counter through the W-bus.

Where is the 4-bit address stored in the Memory Address Register (MAR) sent?
The 4-bit address stored in the MAR is sent to the RAM.

How many memory locations does the Random Access Memory (RAM) of the Simple As Possible (SAP)-1 computer have?
The RAM of the SAP-1 computer has 16 memory locations.

How many bytes is each memory location in the Random Access Memory (RAM) of the Simple As Possible (SAP)-1 computer have?
Each memory location in the RAM of the SAP-1 computer has 8 bytes.

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What does the Instruction Register of the Simple As Possible (SAP)-1 computer do?
The Instruction Register of the SAP-1 computer receives and stores the instruction placed on the bus from the RAM.

What happens to the content of the Instruction Register?
The content of the Instruction Register splits into two nibbles called the upper and lower nibble.

What is the upper nibble and where does it go?
The upper nibble is a two-state output that goes into the Controller-Sequencer.

What is the lower nibble and where does it go?
The lower nibble is a three-state output that is read from the bus when needed.

What does the Controller-Sequencer do in the Simple As Possible (SAP)-1 computer?
In the SAP-1 computer, the Controller-Sequencer sends out signals that control the computer and makes sure things happen only when they're supposed to.

What is the 12-bit output signal of the Controller-Sequencer called?
The 12-bit output signal of the Controller-Sequencer is called the control word.

What does the control word determine?
The control word determines how the registers will react to the next positive clock edge.

What is the format of the control word?
The format of the control word is CON = Cp Ep ~Lm ~CE ~Li ~Ei ~La Eu Su Eu ~Lb ~Lo.

What is the Accumulator in the Simple As Possible (SAP)-1 computer?
In the SAP-1 computer, the Accumulator is an 8-bit buffer register that stores intermediate answers during a computer run.

What are the two outputs of the Accumulator in the Simple As Possible (SAP)-1 computer?
The two outputs of the Accumulator in the SAP-1 computer are:

  1. The two-state output.
  2. The three-state output.

Where does the two-state output of the Accumulator go?
The two-state output of the Accumulator goes to the Adder-Subtractor.

Where does the three-state output of the Accumulator go?
The three-state output of the Accumulator goes to the bus.

What does the Adder-Subtractor do in the Simple As Possible (SAP)-1 computer?
In the SAP-1 computer, the Adder-Subtractor asynchronously adds to or subtracts a value from the Accumulator depending on the value of Su.

What does the Adder-Subtractor make use of in order to perform addition or subtraction?
In order to perform addition or subtraction, the Adder-Subtractor makes use of Two's Complement.

What does the Adder-Subtractor do when Su is low?
When Su is low, the Adder-Subtractor adds the values in the Accumulator and the B-Register.

What does the Adder-Subtractor do when Su is high?
When Su is high, the Adder-Subtractor subtracts the values in the Accumulator and the B-Register.

What does the B-Register in the Simple As Possible (SAP)-1 computer do?
The B-Register in the SAP-1 computer supplies the number to be added or subtracted from the contents of the Accumulator and the Adder-Subtractor.

When does the B-Register retrieve and store data?
The B-Register retrieves and stores data when its available at the bus while Lb is low at the positive clock edge.

What does the Output Register of the Simple As Possible (SAP)-1 computer do?
The Output Register of the SAP-1 computer retrieves and stores the value stored in the Accumulator, typically after an arithmetic operation is performed.

Through what is the answer stored in the Accumulator loaded into the Output Register and when?
The answer stored in the Accumulator is loaded into the Output Register through the W-bus during the next positive clock edge when Ea is high and Lo is low.

What does the Binary Display of the Simple As Possible (SAP)-1 computer do?
The Binary Display of the SAP-1 computer displays the contents of the Output Register.

SAP-1 Instruction Set

What is the instruction set of a computer?
The instruction set of a computer is the basic operations it can perform.

What is the instruction set of the Simple As Possible (SAP)-1 computer?
The instruction set of the SAP-1 computer is:

  • Load - Load data from memory to the Accumulator.
  • Add - Add data from memory to the value in the Accumulator.
  • Subtract - Subtract data from memory from the value in the Accumulator.
  • Output - Load data from the Accumulator to the Output Register.
  • Halt - Stop processing.

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