Contents

1. Overview

2. Using

3. Programs
3.1. Library::HalfAdder
3.2. Library::FullAdder
3.3. Library::Decode
3.4. Library::Mux
3.5. Library::Demux

1. OVERVIEW

The program library is a set of programs that you can use when writing your own programs.

2. USING

You may use a program by using the CALL operator and specifing the program name. Many programs require input that must be placed on the stack using the PUSH operator before calling the program. When the program completes, its output is placed on the stack and may be read using the POP or PEEK operators.

3. PROGRAMS

In the programs below, inputs are listed in the order that they should be pushed onto the stack using the PUSH operator. Outputs are listed in the order that they would be popped off the stack using the POP operator.

3.1. LIBRARY::HALFADDER

The Library::HalfAdder program implements a binary half adder. This program helps illustrate how a computer adds two binary numbers together and is available for educational purposes. The ADD operator implements this functionality and more efficient to use.

Inputs:

B_n -- Bit n from the second binary number.

A_n -- Bit n from the first binary number.

Outputs:

S -- The sum of A_n, B_n, and C_in.

C_out -- The value of the carry resulting from the sum of A_n, B_n, and C_in.

Program Listing:

POP R1
POP R0
AND R0 R1 R3
PUSH R3
XOR R0 R1 R3
PUSH R3

3.2. LIBRARY::FULLADDER

The Library::FullAdder program implements a binary full adder. This program helps illustrate how a computer adds two binary numbers together and is available for educational purposes. The ADD operator implements this functionality and more efficient to use.

Inputs:

C_in -- The value of the carry from the previous call to Library::FullAdder or Library::HalfAdder. If this is the first call to Library::FullAdder, this value should be FALSE.

B_n -- Bit n from the second binary number.

A_n -- Bit n from the first binary number.

Outputs:

S -- The sum of A_n, B_n, and C_in.

C_out -- The value of the carry resulting from the sum of A_n, B_n, and C_in.

Program Listing:

POP R2
POP R1
POP R0
XOR R0 R1 R3
AND R2 R3 R4
AND R0 R1 R5
OR R4 R5 R4
PUSH R4
XOR R2 R3 R4
PUSH R4

3.3. LIBRARY::DECODE

The Library::Decode program implements a 2-to-4 line single bit decoder.

Inputs:

I₀ -- The first bit of the encoded value.

I₁ -- The second bit of the encoded value.

Outputs:

O₀ -- The first bit of the decoded value.

O₁ -- The second bit of the decoded value.

O₂ -- The third bit of the decoded value.

O₃ -- The fourth bit of the decoded value.

Program Listing:

POP R1
POP R0
AND R0 R1 R2
PUSH R2
NOT R0 R2
AND R2 R1 R2
PUSH R2
NOT R1 R2
AND R0 R2 R2
PUSH R2
NAND R0 R1 R2
PUSH R2

3.4. LIBRARY::MUX

The Library::Mux program implements a 4-to-1 line multiplexer.

Inputs:

I₀ -- The first input stream.

I₁ -- The second input stream.

I₂ -- The third input stream.

I₃ -- The fourth input stream.

S₀ -- The first bit of the selector.

S₁ -- The second bit of the selector.

Outputs:

F -- The multiplexed value.

Program Listing:

POP R5
POP R4
POP R3
POP R2
POP R1
POP R0
PUSH R4
PUSH R5
CALL Library::Decode
POP R4
POP R5
POP R6
POP R7
AND R0 R4 R10
AND R1 R5 R11
AND R2 R6 R12
AND R3 R7 R13
OR R10 R11 R14
OR R14 R12 R14
OR R14 R13 R14
PUSH R14

3.5. LIBRARY::DEMUX

The Library::Demux program implements a 1-to-4 line demultiplexer.

Inputs:

F -- The multiplexed stream.

S₀ -- The first bit of the selector.

S₁ -- The second bit of the selector.

Outputs:

O₀ -- The first output stream.

O₁ -- The second output stream.

O₂ -- The third output stream.

O₃ -- The fourth output stream.

Program Listing:

POP R2
POP R1
POP R0
PUSH R1
PUSH R2
CALL Library::Decode
POP R3
POP R4
POP R5
POP R6
OR R0 R6 R7
PUSH R7
OR R0 R5 R7
PUSH R7
OR R0 R4 R7
PUSH R7
OR R0 R3 R7
PUSH R7