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Program Bank Register: Difference between revisions
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The '''Program Bank Register''' (PBR or K) tells the [[65c816]] which [[bank]] to fetch the next opcode from. It is 8 bits wide and is cleared to zero on reset.<sup>[2]</sup> [[PHK]] pushes it onto the [[stack]], but there is no PLK to pull it. | The '''Program Bank Register''' (PBR or K) tells the [[65c816]] which [[bank]] to fetch the next opcode from. It is 8 bits wide and is cleared to zero on reset.<sup>[2]</sup> [[PHK]] pushes it onto the [[stack]], but there is no PLK to pull it. | ||
PBR is affected only by:<sup>[4]</sup> | PBR is affected only by these intructions (and hardware [[interrupt]]s which also zero it) :<sup>[4]</sup> | ||
* [[RTI]] | * [[RTI]] | ||
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* [[JSL]] | * [[JSL]] | ||
* [[JMP]] absolute long | * [[JMP]] absolute long | ||
* [[COP]] (zeros it) | |||
* [[BRK]] (zeros it) | |||
Incrementing the [[program counter]] past FFFFh does not affect PBR.<sup>[4]</sup> | Incrementing the [[program counter]] past FFFFh does not affect PBR.<sup>[4]</sup> | ||
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# section 2.9 on page 7 of 65c816 datasheet, https://westerndesigncenter.com/wdc/documentation/w65c816s.pdf | # section 2.9 on page 7 of 65c816 datasheet, https://westerndesigncenter.com/wdc/documentation/w65c816s.pdf | ||
# Figure 2-3-2 Super FX Memory Map on [https://archive.org/details/SNESDevManual/book2/page/n106 page 2-3-4 of Book II] | # Figure 2-3-2 Super FX Memory Map on [https://archive.org/details/SNESDevManual/book2/page/n106 page 2-3-4 of Book II] | ||
# section 3.4 Program Address Space of 65c816 datasheet | # section 3.4 Program Address Space of 65c816 datasheet (COP and BRK are omitted here, but they are mentioned in section 7.11.1 and 7.11.2) | ||
# [[Eyes & Lichty]], [https://archive.org/details/0893037893ProgrammingThe65816/page/53 page 53] | # [[Eyes & Lichty]], [https://archive.org/details/0893037893ProgrammingThe65816/page/53 page 53] | ||
Revision as of 21:19, 17 August 2024
The Program Bank Register (PBR or K) tells the 65c816 which bank to fetch the next opcode from. It is 8 bits wide and is cleared to zero on reset.[2] PHK pushes it onto the stack, but there is no PLK to pull it.
PBR is affected only by these intructions (and hardware interrupts which also zero it) :[4]
Incrementing the program counter past FFFFh does not affect PBR.[4]
There is also a program bank register on the GSU.[1] It can be used to specify any mapped bank address.[3]
See Also
References
- paragraph 4.5 on page 2-4-5 of Book II
- section 2.9 on page 7 of 65c816 datasheet, https://westerndesigncenter.com/wdc/documentation/w65c816s.pdf
- Figure 2-3-2 Super FX Memory Map on page 2-3-4 of Book II
- section 3.4 Program Address Space of 65c816 datasheet (COP and BRK are omitted here, but they are mentioned in section 7.11.1 and 7.11.2)
- Eyes & Lichty, page 53