ELEC40006-P1-CW/testing/list.txt

Comments:
  R1 holds x, value to be found
  R2 holds head, the memory location of the first element
  R3 holds the number END = 16b'0000100000000000'=0x800 (for comparing, this is the end of the linked list)
  R4 holds the current element in the traversed list
  R5 holds the number 0xB (for jumping to the end)
  R6 holds the number 0x5 (for jumping back)
  A linked list pair is stored as men[N]=value and mem[N+1] = address of next element

(0x0) LDA R1 ##MEMORY_LOCATION_OF_x##                (loads the value to be found, x, into R1)
(0x1) LDA R2 ##MEMORY_LOCATION_OF_head##             (loads the address of the first element into R2)
(0x2) LDA R3 ##MEMORY_LOCATION_OF_END##              (loads a number (0x800) to R3 which is our definition of an end of a linked list)
(0x3) LDA R5 ####MEMORY_LOCATION_CONTAINING_0xB##    (loads a number (0xB) to R5 which is used for jumping to STP, when the element is found or no elements left)
(0x4) LDA R6 ####MEMORY_LOCATION_CONTAINING_0x5##    (loads a number (0x5) to R6 which is used for jumping to back, if current element is not the required element and there are still elements left)
(0x5) LDR R4 R2                                      (loads R4 using data from the memory address which is the value in R4)
(0x6) JC3 R5 R4 R1                                   (jumps to the end ('STP') if R4 (current element) is equal to R1 (required element))
(0x7) ADO R2                                         (adds one to R2, which when completed contains the address of the address of next element in the linked list)
(0x8) LDR R2 R2                                      (loads the address of the next element into R2, thus updating the current head)
(0x9) JC3 R5 R2 R3                                   (jumps to the end ('STP') if R2 (current head) is equal to R3 (end of list)
(0xA) JMP R6                                         (jumps to value stored in R4 () which repeats this process)
(0xB) STP                                            (program end)


Example that can be used with the instruction generator program:
LDA R1 0
LDA R2 1
LDA R3 2
LDA R5 3
LDA R6 4
LDR R4 R2
JC3 R5 R4 R1
ADO R2
LDR R2 R2
JC3 R5 R2 R3
JMP R6
STP

Requires setting the following data memory locations:
Set location '0' to value of x;
Set location '1' to value of head;
Set location '2' to value of 0x800 (end of linked list)
Set location '3' to value of 0xB (end of program, STP);
Set location '4' to value of 0x5; (going back)
Create a linked list that starts at 'head' memory location