We've just updated MediaWiki and its underlying software. If anything doesn't look or work quite right, please mention it to us. --RanAS

Program Counter Relative Addressing

From SnesLab
Revision as of 04:44, 9 August 2024 by Xetheria (talk | contribs) (→‎Syntax: explain nearlabel)
(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)
Jump to: navigation, search

Program Counter Relative Addressing is supported by nine instructions on the 65c816:

  • BCC (opcode 90)
  • BCS (opcode B0)
  • BEQ (opcode F0)
  • BMI (opcode 30)
  • BNE (opcode D0)
  • BPL (opcode 10)
  • BRA (opcode 80)
  • BVC (opcode 50)
  • BVS (opcode 70)

All of which are two bytes long.

The effective address is generated by sign-extending the 8-bit operand to 16 bits and then adding it to the program counter. The program bank register remains the same.

Syntax

BRA nearlabel

Where nearlabel is in the range of -128 to 127 bytes away from the next opcode after BRA.

See Also

References

Retrieved from "https://sneslab.net/mw/index.php?title=Program_Counter_Relative_Addressing&oldid=19920"