NICASM-Required-Files

This branch contains all files that are required to use the NICASM Simulated Processors

Credits

Work on this project was primarily completed as follows:

Architecture Design : Nicholas Deckhut

Assembler Programming : Brian Donald

NICASM was loosely based on the LC3, with several changes made throughout its creation.

Instructions

This program works in tandem with a software called Logisim, the executable can be found here.

Assembling a program

The software will run from the BetterAssembler class, and requires the following command line syntax:

  java site.projectname.Assembler [-debug] filename

Example .nic files can be found in asmFiles

Executing a Program

Open logisim
Load Computer.circ.
Right click the memory object labeled "MEM.HDD", and select "Load Image." Select the image you have assembled with BetterAssembler (Output file will be stored next to the original in a .nicp file)
Ensure Simulate>Ticks Enabled is enabled (Keyboard Shortcut CTRL+K)
Set Tick Speed to desired option Simulate>Tick Speed
Turn the NIC on, power key is on the upper left
Interact with program as needed
- Keyboard input is required when the ASK indicator is lit
- Keyboard is a white bar located in the upper-right, near the Clock and LD.READ tags, click on it to start typing, simply click elsewhere to stop

A Quick and Dirty intro to NICASM Syntax

Like other assembly-like languages, NICASM has very rudimentary syntax, consisting of at most 3 or 4 parts per line. The most common are:

Command (ADD, AND, BR, JMP, etc.)
- Declares which operation this line performs
- Required on (nearly) every line.
Register (R0,R1,R2,R3)
- Refers to a value stored in a CPU Register
- NICASM has 8 registers available (0-7)
Immediate Value (#5,xF,etc.)
- Refers to a direct value, limits vary based on command
Variable ($MYVARNAME)
- Used to spare a headache, can be referred to by LD,LDI,LEA,ST,STI,and .FILL)
Label (*Label)
- Used to name a line, makes BR much simpler

A not as Quick and much Dirtier intro to NICASM Syntax

Commands

Glossary

DR = Destination Register
SRX = Source Register 0-7
IMMX = X-bit Immediate Value (-1*((2^x)/2-1) -> ((2^x)/2-1)) ), can be Decimal(#) or Hexadecimal(x) (Example, IMM5 can be #-15 -> #15)
PC = Current memory address of program
PC' = Next memory address of program (Most often PC+1)

ADD DR, SR1, [SR2|IMM5]
> Adds SR1 and [SR2|IMM5] and saves result in DR
> ADD R0 R0 R1
> ADD R0 R0 #15

AND DR, SR1, [SR2|IMM5]
> Bitwise and of SR1 and [SR2|IMM5] and saves result in DR
> AND R0 R0 R1
> AND R0 R0 xF

BR[n][z][p] [Label|IMM8]
> Jumps execution to line specified by Label, or line offset specified by IMM8
> n jumps if value is negative, z jumps if value is zero, p jumps if value is positive, order matters here, but they are all optional
> For Immediate Value the new PC will be PC'+IMM8
> BRn .Main
> BRp #-15 \*Goes back 14 Lines (-15+PC' is the same as -14+PC)\*

JMP BR
> Always jumps program to line specified in BR (Base Register)
> JMP R7 \*This command is identical to RET\*

JSR Label
> Jumps program to Label, used to create functions
> Stores current address in R7
> JSR .Main

JSRR BR
> Identical to JSR, uses Register for offset rather than label
> Stores current address in R7
> JSRR R0

LD DR, [Variable|IMM8]
> Loads value stored at variable or immediate value into Destination Register
> LD R0 $MyVarName
> LD R0 #127

LDI DR, Variable
> Treats variable as pointer and loads that value into DR
> LDI R0 $MyVarName

LDR DR, SR, IMM6
> Loads value at MEM[SR+IMM6] into DR
> LDR R0 R5 #-1

LEA DR, [Variable|IMM8]
> Loads value of PC'+IMM8 or Variable into DR
> LEA R0 #-100

NOT DR, SR
> Bitwise not of SR into DR
NOT R0 R0

RET
> Jumps program to address in R7, if used with JSR and JSRR it can form rudimentary functions
> RET

ST DR, [Variable|IMM8]
> Stores value of DR in variable, or MEM[PC'+IMM8]
> ST R0 $MyVarName
> ST R1 xF3

STI DR, Variable
> Treats variable as pointer and stores the value of DR there
> i.e. if $Pointer = x0001, and R0 = #10, then
> STI R0 $Pointer
> Would make MEM[x0001] = #10

STR DR, SR, IMM6
> Stores value in DR at MEM[SR+IMM6]
> STR R0 R1 #6

TRAP
> Not used

.FILL
> Fills the line with a IMM16, most commonly used for variables

.BLK
> Blocks of a portion of lines as empty, good for creating space for array variables
> Shouldn't be used with large values, chunk into multiple smaller .BLKs

READ DR
> Gets a value from the user, and stores it in the given register

PRINT SR
> Prints the character in the given register

Shorthand commands

These commands are given as a way to make common tasks much easier, because these add new lines, it is #extremely# recommended to use variables over offset values when using them in your program. This is not a comprehensive list, the stack-specific shorthand commands have been left out, simply because they are not working properly at this time.

.SUB DR, SR1, SR2
> Subtracts SR2 from SR1 and stores into DR

.MUL DR, SR1, [SR2|IMM5]
> Multiplies SR1 by SR2|IMM5 and stores in DR

.SET DR, [IMM16|Variable]
> Sets DR to the IMM16 or Variable value

.COPY DR, SR1
> Copies value from SR1 into DR
> Equivalent to ADD DR, SR1, #0, but makes code easier to read

.ZERO DR
> Sets DR to 0
> Equivalent to AND DR,DR,#0, but makes code easier to read

.MAIN
> Defines entry point of program

.PRINTS [Variable|IMM16]
> Prints a string, stops upon reaching a negative value

.READS IMM16
> Reads a string, stops reading on Return Key
> String gets stored at IMM16

ItsMeBrianD/NICASM