Commodore Plus 4 - Page 294

383 Machine Language on the Commodore Plus/4
SOOC 00
200D EE
2010 4C
BRK
19 PP DTC &FF19
OE CE JMP $CEOE
Stop processing.
Increment the border color.
Jump to normal IRQ processing.
After you execute this program (by typing G 2000), the processing of an
interrupt increments the border color before proceeding normally. When you are
finished with this example, reset the computer by typing G FFF6 to restore the
IRQ vector to its default value.
STA—Store Value in Accumulator into Memory
The value currently in the accumulator is placed in the location specified by the
operand.
Example:
Operation: A — M
Addressing Mode
Zero page
Zero page, X
Absolute
Absolute, X
Absolute, Y
(Indirect, X)
(Indirect), Y
Syntax
STA $hh
STA $hh,X
STA Shhhh
STA $hhhh,X
STA $hhhh,Y
STA ($hh,X)
STA ($hh),Y
Flags Affected: None
Opcode
85
95
8D
9D
99
81
91
Bytes
2
2
3
3
3
2
2
Cycles
3
4
4
5
5
6
6
The value of the accumulator is not altered, and the flags are not altered.
The characters on the top line of the screen are copied to the second line of the
screen. Each value is transferred by loading it into the accumulator and storing it
to the destination with the STA instruction.
. 2000 A2 27 LDX #$27 .X indexes the line.
. 2002 BD 00 OC LDA $0C00*X Load the accumulator with next
character.
. 2005 9D 28 OC STA $0C28,X
2008 CA
2009 10 P7
200B 00
DEX
BPL $2002
BRK
Store the value in the accumulator on
the second line.
Decrement the index register.
If there is more to do, go back.
Stop processing.
If executing the BRK instruction causes the screen to scroll, the result of the
program will not be seen. To avoid this, clear the screen before executing the
program.