Commodore Plus 4 - Page 277

The 6502 Microprocessor 268
INY—Increment the Y Register by 1
The value currently in the Y register is incremented by 1.
Operation: Y+ 1 - Y Flags Affected: N, Z
Addressing Mode Syntax Opcode Bytes Cycles
Implied INY C8 J 2
The value stored in the Y register is increased by 1. If the result is negative, the
N flag is set to 1; otherwise it is cleared to 0. If the result is zero, the Z flag is set to
1; otherwise it is cleared to 0.
Example: In this example, the first byte in $8000-$80FF containing a value of $EA is
located. The Y register is used as the index, and the INY instruction updates it.
. 2000 A0 00 LDY #$00 Initialize . Y to zero.
. 2002 A9 EA LDA #$EA Load .A with the value to look for.
. 2004 D9 00 80 CMP $8000,Y Compare with the current location.
. 2007 FO 03 BEQ $2000 If equal, quit.
. 2009 C8 INY Update the index register.
. 200A DO F8 BNE $2004 If there are more locations to search,
go back.
. 200C 00 BRK Stop processing.
When the BRK instruction is executed, the value of the Y register when an $EA
was found (or a zero if none was found) is displayed.
JMP—Jump to a New Location
The address specified in the operand is transferred to the program counter, and
processing continues with the instruction located at that address.
Operation:
Addressing
Absolute
Indirect
(FC +
Mode
1)
- PCL
Syntax
JMP Shhhh
JMP (Shhhh)
Flags Affected:
Opcode Bytes
4C 3
6C 3
None
Cycles
3
5