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LDB (Super FX): Difference between revisions
From SnesLab
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where m can be from 0~11 | where m can be from 0~11 | ||
==== Example ==== | |||
Let: | |||
D<sub>reg</sub> : R<sub>7</sub> | |||
R<sub>1</sub> = 3482h | |||
RAMBR : 70h | |||
(70:3482h) = 51h | |||
After LDB (R<sub>1</sub>) is executed: | |||
R<sub>7</sub> = 0051h | |||
=== See Also === | === See Also === | ||
Revision as of 22:18, 8 July 2024
| Basic Info | |||||||
|---|---|---|---|---|---|---|---|
| Addressing Mode | Opcode | Length | ROM Speed | RAM Speed | Cache Speed | ||
| Implied Indirect | 3D4m | 2 byte | 11 cycles | 13 cycles | 6 cycle | ||
| Flags Affected | ||||||||
|---|---|---|---|---|---|---|---|---|
| B | ALT1 | ALT2 | O/V | S | CY | Z | ||
| 0 | 0 | 0 | . | . | . | . | ||
LDB (Load Byte) is a Super FX instruction that loads one byte from the Game Pak and stores it in the low byte of the destination register. The high byte of the destination register is zeroed.
Part of the reason why LDB takes so many cycles is that the GSU waits for data to be loaded from game pak ram.
Syntax
LDB (Rm)
where m can be from 0~11
Example
Let:
Dreg : R7 R1 = 3482h RAMBR : 70h (70:3482h) = 51h
After LDB (R1) is executed:
R7 = 0051h
See Also
External Links
- Official Super Nintendo development manual on LDB: 9.45 on Page 2-9-64 of Book II
- example: Page 2-9-65, lbid.