1. Write one line of HCS12 assembly language to do the following. (Note that add

Question

1. Write one line of HCS12 assembly language to do the following. (Note that adds and subtracts are without carry.)
a. Clear register A
b. Add the number hexadecimal C7 to register B
c. Add the contents of memory location $0054 to register A
d. Subtract the contents of memory location $16CF from register B
e. Fetch data from the memory location indicated by register X and load it into register A
f. Fetch data from the memory location indicated by register Y plus 8 and add it to register B
g. Increment register X by 12 and then use it as the address to fetch data and load it into register A
h. Use register Y as an address to fetch data and add it to register B, then decrement Y by 8
i. Move 1 word (16 bits) from the location indicated by register X to the location indicated by register Y.
2. Briefly explain what each line of HCS12 assembly language does:
a. CLRB
b. INCA
c. SUBA #7
d. TFR X,Y
e. EXG A,B

Explanation / Answer

1.

(a) CLRA
(b) ADDB C7
(c) ADDA #0054
(d) SUBB #16CF
(e) LDAX
STAA
(f) LDAY+LDA8
   STAB

2.
(a) CLRB is used to clear register B
(b) INCA is used toincrement register A
(c) SUBA #7 is used to subtract a number from address 7 to A
(d) TFR X,Y is transfer from register X to Y
(e) EXG A,B menas exchange data between A and B

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