EECS 388 HW #3
Due: March 4
Problems from textbook
Q1: Page 70: Challenging โ 7 (20 points)
Write a program segment starting at $C100 that checks bits 0 and 2 of address $D000 and
jumps to $C0CC if both bits are clear.
This task is easily accomplished using the BRCLR instruction. We are interested in bits 0
and 2, which gives us the 8-bit mask 00000101 ($05). Therefore:
ORG $C100
LDX #$D000
BRCLR 0,X,$05,$C0CC
SWI
Q2: Page 116: Advanced โ 3 (25 points)
Write a program using a subroutine to copy a table from one location to another. A
partially completed program is given next. Write a program by filling in locations where
only comments appear.
Note 1: when we save the CPU registers, we have to make sure to restore them in reverse
order to align the values properly and to make sure they go back to their proper places.
Note 2: FDB and FCB are not identical to EQU; when you load the values into a register,
you do not use the immediate operator โ#โ.
* Copying a table using a subroutine
Data Section
ORG $0000
TAB1 FDB $D100 ; address of the first table
TAB2 FDB $D300 ; address of the second table
TABL FCB $FF ; table length
* main program
ORG $C100
LDS #$8000 ; initialize the stack pointer
LDAA TABL ; load the table length to acc A
LDX TAB1 ; load table 1 address to X
LDY TAB2 ; load table 2 address to Y
JSR COPYT ; call the subroutine
SWI ; stop subroutine
ORG $4500
