About the Assembler Activity.
The Aeembler Activity allows small programs to be entered with the assembly language based
on the assembly language used by AQA n its Computer Science exams. It uses an input mechanism which restricts the entry so that only
valid code can be entered as well as the option to enter code using text entry.
The code can then be run using the Session tab. This allows for memory data to be entered and then for the code to be run. There is
also the option to run the code line by line that shows the registers and flags being updated at each point.
This activity can be used to give a better understanding of Assembly language and how it works.
The machine code tab simulates how a program is loaded into memory and run. The machine code instruction set is loosely based on
the ARM instruction set, using where possible, similar opcode values. Each instruction is stored in three bytes. One for the opcode and
two for the operands. (Three 4-bit values for the registers or two 4-bit values for the registers and one 8-bit value for the data).
Note that all values are restricted to a byte and all values and results are therefore taken as the modulo of 256.
Note that this is a testing release. Please contact me is you find any issues.
Note that this is a testing release. Please contact me is you find any issues.
Session - Processing the Assembler in Denary
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Register Values
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Flag Values
General Memory
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Set Memory Value
Last Instruction
Assembly Code
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Machine Code Session
Register Values
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Current Instruction (Hexadecimal)
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Flag Values
General Memory (Values in denary)
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Code Memory (Values in hexadecimal)
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Assembly Language and Machine Code
Label Addresses
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There are a number of example programs which can be loaded in to illustrate how Assembly-Code can be written and run using this application.
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Add
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Adds the values in memory locations 0 and 1 together.
Stores the result in memory location 2.
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Count to 10
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Counts through the numbers from 1 to 10, using register 0 to store the values.
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multiply
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Multiplies the values in memory locations 0 and 1 together.
Stores the result in memory location 2.
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Power of 2
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Calculates 2 to the power of the value stored in memory location 0 using the LSL command.
Stores the result in memory location 1.
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Divide by 16
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Divides the value in memory locations 0 by 16.
Stores the result in memory location 1.
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Div and Mod
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Does an integer division on the value in memory location 0 by the value in memory location 1.
Stores the integer result of the divide in memory location 2.
Stores the remainder in memory location 3.
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Is Even
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Does a bitwise logical AND with 1 to find whether the value in memory location 0 is odd or even..
Stores the result in register 0 (1 for odd and 0 for even).
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A and B or C
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Does a bitwise logical AND between the values in memory locations 0 and 1 and then does a bitwise logical OR between the result and the value in memory location 2.
Stores the result in memory location 3.
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NAND
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Does a bitwise logical AND between the values in memory locations 0 and 1.
Stores the result in memory location 2.
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Triangular Numbers
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Calculates the triangular number of the value in memory location 0.
Stores the result in memory location 1.
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