1. Start your program at address $8500. To do this you need to inform the assembler, through the EQU and ORG assembler directives, that you want your program to start at $8500. This can be done as shown below:
(leave 2 tab-spaces) ROMSTART EQU $8500
ORG ROMSTART
The first line above equates the string ROMSTART with $8500. If you mention ROMSTART in any subsequent part of your program, it will be replaced with $8500 during execution.
The second line tells the assembler that the assembly process should now proceed from the address specified by ROMSTART. (ORG can be used multiple times in your program if you wish to alter the assembly flow).
2. Read a set of three hexadecimal numbers located in memory addresses $4000, $4001, and $4002 and store them to memory locations $0800, $0801, and $0802, respectively.
3. Read the three values from the new memory locations and check each one against a threshold value of $55. You can use the EQU directive at the beginning of the program to declare the threshold as follows:
THRESH EQU $55
4. If the value stored in memory location $0800 is higher (unsigned numbers) than the threshold value, compute the sum of the first five natural numbers. Store the number back to the memory location $0800.
5. If the value stored in memory location $0801 is higher (unsigned numbers) than the threshold value, store $00 to the same memory location.
6. If the value stored in memory location $0802 is higher (unsigned numbers) than the threshold value, subtract $10 from the value stored in the memory location $0802 and store the resulting value back to the same memory location.