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SBC (Super FX): Difference between revisions
From SnesLab
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'''SBC''' (SuBtract with Carry) is a [[Super FX]] instruction that performs a subtraction with regards to the [[CY|carry flag]]. | '''SBC''' (SuBtract with Carry) is a [[Super FX]] instruction that performs a subtraction with regards to the [[CY|carry flag]]. | ||
Unlike [[ADD (Super FX)]], [[ADC (Super FX)]] and [[SUB (Super FX)]], this one can only be used with registers, not with constant values since since the ALT3 version of SUB is a [[CMP (Super FX)]] instead. | Unlike [[ADD (Super FX)]], [[ADC (Super FX)]] and [[SUB (Super FX)]], this one can only be used with registers, not with constant values since since the ALT3 version of SUB is a [[CMP (Super FX)]] instead. | ||
The [[ALT0]] state is restored. | |||
The source and destination registers should be specified in advance using [[WITH]], [[FROM]], or [[TO]]. Otherwise, R<sub>0</sub> serves as the default. | The source and destination registers should be specified in advance using [[WITH]], [[FROM]], or [[TO]]. Otherwise, R<sub>0</sub> serves as the default. | ||
Revision as of 00:22, 13 July 2024
| Basic Info | |||||||
|---|---|---|---|---|---|---|---|
| Addressing Mode | Opcode | Length | ROM Speed | RAM Speed | Cache Speed | ||
| Implied (type 1) | 3D6n | 2 bytes | 6 cycles | 6 cycles | 2 cycle | ||
| Flags Affected | ||||||||
|---|---|---|---|---|---|---|---|---|
| B | ALT1 | ALT2 | O/V | S | CY | Z | ||
| 0 | 0 | 0 | ||||||
SBC (SuBtract with Carry) is a Super FX instruction that performs a subtraction with regards to the carry flag. Unlike ADD (Super FX), ADC (Super FX) and SUB (Super FX), this one can only be used with registers, not with constant values since since the ALT3 version of SUB is a CMP (Super FX) instead.
The ALT0 state is restored.
The source and destination registers should be specified in advance using WITH, FROM, or TO. Otherwise, R0 serves as the default.
Syntax
SBC Rn
Example
Let:
Sreg : R4 Dreg : R6 R4 = 5682h R5 = 3609h CY = 1
After executing SBC R5:
R6 = 2079h CY = 0
See Also
Reference
- 9.78 on page 2-9-108 of Book II of the official Super Nintendo development manual