We've just updated MediaWiki and its underlying software. If anything doesn't look or work quite right, please mention it to us. --RanAS
GETBS (Super FX): Difference between revisions
From SnesLab
(missing b) |
|||
| (20 intermediate revisions by the same user not shown) | |||
| Line 2: | Line 2: | ||
!colspan="8"|Basic Info | !colspan="8"|Basic Info | ||
|+ | |+ | ||
|'''Addressing Mode''' | |||
|'''Opcode''' | |'''Opcode''' | ||
|'''Length''' | |'''Length''' | ||
| Line 8: | Line 9: | ||
|'''Cache Speed''' | |'''Cache Speed''' | ||
|+ | |+ | ||
|[[Implied]] (type 1) | |||
|3FEF | |3FEF | ||
|2 bytes | |2 bytes | ||
|6 to 10 cycles | |6 to 10 cycles | ||
|6 to 9 cycles | |6 to 9 cycles | ||
|2 to 6 | |2 to 6 cycles | ||
|} | |} | ||
| Line 18: | Line 20: | ||
!colspan="9"|Flags Affected | !colspan="9"|Flags Affected | ||
|+ | |+ | ||
|B | |[[B Flag|B]] | ||
|[[ALT1]] | |[[ALT1]] | ||
|[[ALT2]] | |[[ALT2]] | ||
|[[O/V]] | |[[O/V]] | ||
|S | |[[Sign Flag|S]] | ||
|[[CY]] | |[[CY]] | ||
|Z | |[[Zero Flag|Z]] | ||
|+ | |+ | ||
|0 | |0 | ||
| Line 35: | Line 37: | ||
|} | |} | ||
'''GETBS''' is a [[Super FX]] instruction that loads one byte from the [[ROM buffer]] into the low byte of the [[destination register]]. Every bit of the high byte | '''GETBS''' (Get Signed Byte) is a [[Super FX]] instruction that loads one byte from the [[ROM buffer]] into the low byte of the [[destination register]]. Every bit of the destination register's high byte becomes whatever bit 7 of that loaded byte is. | ||
The reason the cycle times can vary is because of the ROM buffer. | The reason the cycle times can vary is because of the [[ROM buffer]]. The [[ALT0]] state is restored. | ||
The destination register should be specified in advance using [[WITH]] or [[TO]]. Otherwise, R<sub>0</sub> serves as the default. The [[source register]] is ignored. | |||
==== Syntax ==== | |||
<pre> | |||
GETBS | |||
</pre> | |||
==== Example ==== | |||
Let: | |||
(ROM buffer) = 85h | |||
D<sub>reg</sub> : R<sub>8</sub> | |||
After executing GETBS: | |||
R<sub>8</sub> = ff85h | |||
[[File:gsu getbs.png]] | |||
=== See Also === | === See Also === | ||
| Line 43: | Line 61: | ||
* [[GETBL]] | * [[GETBL]] | ||
* [[GETBH]] | * [[GETBH]] | ||
* [[GETC]] | |||
* [[ALT3]] | |||
=== External Links === | === External Links === | ||
* Official Super Nintendo development manual on GETBS: [https://archive.org/details/SNESDevManual/book2/page/n211 | * Official Super Nintendo development manual on GETBS: 9.38 on [https://archive.org/details/SNESDevManual/book2/page/n211 page 2-9-55 of Book II] | ||
* example: [https://archive.org/details/SNESDevManual/book2/page/n212 page 2-9-56 of Book II], lbid | |||
[[Category:ASM]] | [[Category:ASM]] | ||
| Line 51: | Line 72: | ||
[[Category:Data Transfer Instructions]] | [[Category:Data Transfer Instructions]] | ||
[[Category:Two-byte Instructions]] | [[Category:Two-byte Instructions]] | ||
[[Category:Expects Sreg/Dreg Prearranged]] | |||
Latest revision as of 09:19, 31 July 2024
| Basic Info | |||||||
|---|---|---|---|---|---|---|---|
| Addressing Mode | Opcode | Length | ROM Speed | RAM Speed | Cache Speed | ||
| Implied (type 1) | 3FEF | 2 bytes | 6 to 10 cycles | 6 to 9 cycles | 2 to 6 cycles | ||
| Flags Affected | ||||||||
|---|---|---|---|---|---|---|---|---|
| B | ALT1 | ALT2 | O/V | S | CY | Z | ||
| 0 | 0 | 0 | . | . | . | . | ||
GETBS (Get Signed Byte) is a Super FX instruction that loads one byte from the ROM buffer into the low byte of the destination register. Every bit of the destination register's high byte becomes whatever bit 7 of that loaded byte is.
The reason the cycle times can vary is because of the ROM buffer. The ALT0 state is restored.
The destination register should be specified in advance using WITH or TO. Otherwise, R0 serves as the default. The source register is ignored.
Syntax
GETBS
Example
Let:
(ROM buffer) = 85h Dreg : R8
After executing GETBS:
R8 = ff85h
See Also
External Links
- Official Super Nintendo development manual on GETBS: 9.38 on page 2-9-55 of Book II
- example: page 2-9-56 of Book II, lbid