Instruction Set Nomenclature
Status Register (SREG)
- SREG
- Status Register
- C
- Carry Flag
- Z
- Zero Flag
- N
- Negative Flag
- V
- Two’s complement overflow indicator
- S
- N ⊕ V, for signed tests
- H
- Half Carry Flag
- T
- Transfer bit used by BLD and BST instructions
- I
- Global Interrupt Enable/Disable Flag
Registers and Operands
- Rd:
- Destination (and source) register in the Register File
- Rr:
- Source register in the Register File
- R:
- Result after instruction is executed
- K:
- Constant data
- k:
- Constant address
- b:
- Bit in the Register File or I/O Register (3-bit)
- s:
- Bit in the Status Register (3-bit)
- X,Y,Z:
- Indirect Address Register (X=R27:R26, Y=R29:R28, and Z=R31:R30)
- A:
- I/O location address
- q:
- Displacement for direct addressing (6-bit)