Write the corresponding S19 file for the code below ORG 0080

Write the corresponding S19 file for the code below:

ORG $0080

Sum: DS.B 1

ORG $FC00

Start: lda Ax

sub #$AB

sta Sum

Done: bra Done

Ax: DC.B $12

ORG $FFFE

DC.W Start

Solution

1) ORG $0080

Explination:

org Set starting value of location counter org $0080 where code or data will go

2) Sum: DS.B 1

Explination:

ds[.size] Allocate specified number of table: ds.w 1 storage spaces. size is the same as for dc directive

3) ORG $FC00

Explination:

org Set starting value of location counter org $FC00 where code or data will go

4) Start: lda Ax

Explination:

LDA copies the data byte into accumulator from the memory location specified by the 16-bit address

5) sub #$AB

Explination:

The sub instruction stores in the value of its first operand the result of subtracting the value of its second operand from the value of its first operand

6) sta Sum

Explination:

STA copies the data byte from the accumulator in the memory location specified by 16-bit address

7) Done: bra Done

Explination:

BRA is a relative jump from current position to anywhere within +1023 and -1024 locations

8) Ax: DC.B $12

Explination:

The DCB directive allocates one or more bytes of memory, and defines the initial runtime contents of the memory.

9) ORG $FFFE

Explination:

org Set starting value of location counter org $FFFE where code or data will go

10) DC.W Start

Explination:

DC.B - Define constant in memory of length of one byte. This assigns a memory address to a constant and initializes it to the constant