BBC (SPC700): Difference between revisions
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'''BBC''' (Branch on Bit Clear) is an [[SPC700]] instruction that performs a branch when a bit in the [[direct page]] is clear. The index to the direct page byte that bit lives in is the first operand byte. Which bit within that byte is specified by the top 3 bits of the opcode. The target relative address to jump to is the second operand byte. | '''BBC''' (Branch on Bit Clear) is an [[SPC700]] instruction that performs a branch when a bit in the [[direct page]] is clear. The index to the direct page byte that bit lives in is the first operand byte. Which bit within that byte is specified by the top 3 bits of the opcode. The target relative address to jump to is the second operand byte. In Nintendo's manual, the high nybble of the opcode is called y. | ||
In assembly source, the two operands appear in the same order that they do in the instruction stream. | In assembly source, the two operands appear in the same order that they do in the instruction stream. |
Revision as of 04:40, 8 July 2024
Basic Info | |||||||
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Addressing Mode | Opcode | Length | Speed | ||||
Direct Page Bit Relative | 13 | 3 byte | when condition is false: 5 cycles
when condition is true: 7 cycles |
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Direct Page Bit Relative | 33 | 3 byte | when condition is false: 5 cycles
when condition is true: 7 cycles |
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Direct Page Bit Relative | 53 | 3 byte | when condition is false: 5 cycles
when condition is true: 7 cycles |
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Direct Page Bit Relative | 73 | 3 byte | when condition is false: 5 cycles
when condition is true: 7 cycles |
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Direct Page Bit Relative | 93 | 3 byte | when condition is false: 5 cycles
when condition is true: 7 cycles |
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Direct Page Bit Relative | B3 | 3 byte | when condition is false: 5 cycles
when condition is true: 7 cycles |
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Direct Page Bit Relative | D3 | 3 byte | when condition is false: 5 cycles
when condition is true: 7 cycles |
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Direct Page Bit Relative | F3 | 3 byte | when condition is false: 5 cycles
when condition is true: 7 cycles |
Flags Affected | |||||||
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N | V | P | B | H | I | Z | C |
. | . | . | . | . | . | . | . |
BBC (Branch on Bit Clear) is an SPC700 instruction that performs a branch when a bit in the direct page is clear. The index to the direct page byte that bit lives in is the first operand byte. Which bit within that byte is specified by the top 3 bits of the opcode. The target relative address to jump to is the second operand byte. In Nintendo's manual, the high nybble of the opcode is called y.
In assembly source, the two operands appear in the same order that they do in the instruction stream.
No flags are affected.
Syntax
BBC dp, bit, rel
See Also
External Links
- Official Super Nintendo development manual on BBC: Table C-15 Appendix C-8 of Book I