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Direct Page Bit Relative Addressing: Difference between revisions
From SnesLab
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Both of which are three bytes long: | Both of which are three bytes long: | ||
* The first byte is the opcode, as usual. The opcode's top 3 bits address which bit to test within a particular direct page byte. | * The first byte is the opcode, as usual. The opcode's top 3 bits address which bit to test within a particular [[direct page]] byte. | ||
* The middle byte is which direct page location the bit to test lives in. | * The middle byte is which direct page location the bit to test lives in. | ||
* The last byte is the target relative address to conditionally jump to. | * The last byte is the target relative address to conditionally jump to. | ||
Latest revision as of 21:37, 5 January 2025
Direct Page Bit Relative Addressing is an addressing mode supported by the SPC700, used by these instructions:
Both of which are three bytes long:
- The first byte is the opcode, as usual. The opcode's top 3 bits address which bit to test within a particular direct page byte.
- The middle byte is which direct page location the bit to test lives in.
- The last byte is the target relative address to conditionally jump to.
Syntax
BBS dp, bit, rel BBC dp, bit, rel
See Also
Reference
- Figure 3-8-3 Memory Access Addressing Effective Address on page 3-8-9 of Book I of the official Super Nintendo development manual