Program Bank Register

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]

• RTI
• RTL
• JML
• JSL
• JMP absolute long
• COP (zeros it)
• BRK (zeros it)

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

• Data Bank Register
• LJMP

References

1. paragraph 4.5 on page 2-4-5 of Book II
2. section 2.9 on page 7 of 65c816 datasheet, https://westerndesigncenter.com/wdc/documentation/w65c816s.pdf
3. Figure 2-3-2 Super FX Memory Map on page 2-3-4 of Book II
4. 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)
5. Eyes & Lichty, page 53