We've just updated MediaWiki and its underlying software. If anything doesn't look or work quite right, please mention it to us. --RanAS
GETB (Super FX): Difference between revisions
From SnesLab
(sreg ignored) |
|||
| (19 intermediate revisions by 2 users 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) | |||
|EF | |EF | ||
|1 byte | |1 byte | ||
|3 to 8 cycles | |3 to 8 cycles | ||
|3 to 9 cycles | |3 to 9 cycles | ||
|1 to 6 | |1 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 36: | Line 38: | ||
'''GETB''' (Get Byte) is a [[Super FX]] instruction that loads one byte from the [[ROM buffer]] into the low byte of the [[destination register]]. The high byte of the destination register is zeroed. | '''GETB''' (Get Byte) is a [[Super FX]] instruction that loads one byte from the [[ROM buffer]] into the low byte of the [[destination register]]. The high byte of the destination register is zeroed. | ||
R<sub>14</sub> serves as the ROM address pointer. | |||
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> | |||
GETB | |||
</pre> | |||
==== Example ==== | |||
Let: | |||
ROM buffer = 0075h | |||
D<sub>reg</sub> : R<sub>0</sub> | |||
After executing GETB: | |||
R<sub>0</sub> = 0075h | |||
[[File:gsu_getb.png]] | |||
=== See Also === | === See Also === | ||
* [[GETBH]] | * [[GETBH]] | ||
* [[GETBL]] | |||
* [[GETBS]] | * [[GETBS]] | ||
* [[GETC]] | |||
* [[ROMB]] | * [[ROMB]] | ||
=== External Links === | === External Links === | ||
* Official Super Nintendo development manual on GETB: [https://archive.org/details/SNESDevManual/book2/page/n205 Page 2-9-49 of Book II] | * Official Super Nintendo development manual on GETB: 9.35 on [https://archive.org/details/SNESDevManual/book2/page/n205 Page 2-9-49 of Book II] | ||
* example: [https://archive.org/details/SNESDevManual/book2/page/n206 page 2-9-50 of Book II], lbid | |||
* page 2-7-1 of Book II, lbid. | |||
[[Category:ASM]] | [[Category:ASM]] | ||
| Line 49: | Line 75: | ||
[[Category:Data Transfer Instructions]] | [[Category:Data Transfer Instructions]] | ||
[[Category:One-byte Instructions]] | [[Category:One-byte Instructions]] | ||
[[Category:Expects Sreg/Dreg Prearranged]] | |||
Latest revision as of 20:21, 30 July 2024
| Basic Info | |||||||
|---|---|---|---|---|---|---|---|
| Addressing Mode | Opcode | Length | ROM Speed | RAM Speed | Cache Speed | ||
| Implied (type 1) | EF | 1 byte | 3 to 8 cycles | 3 to 9 cycles | 1 to 6 cycles | ||
| Flags Affected | ||||||||
|---|---|---|---|---|---|---|---|---|
| B | ALT1 | ALT2 | O/V | S | CY | Z | ||
| 0 | 0 | 0 | . | . | . | . | ||
GETB (Get Byte) is a Super FX instruction that loads one byte from the ROM buffer into the low byte of the destination register. The high byte of the destination register is zeroed.
R14 serves as the ROM address pointer.
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
GETB
Example
Let:
ROM buffer = 0075h Dreg : R0
After executing GETB:
R0 = 0075h
See Also
External Links
- Official Super Nintendo development manual on GETB: 9.35 on Page 2-9-49 of Book II
- example: page 2-9-50 of Book II, lbid
- page 2-7-1 of Book II, lbid.