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PEI: Difference between revisions
From SnesLab
(push order) |
(works in emulation mode) |
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No flags are affected. | No flags are affected. | ||
PEI works even in [[emulation mode]]. | |||
==== Syntax ==== | ==== Syntax ==== | ||
Latest revision as of 23:16, 12 August 2024
| Basic Info | |||||||
|---|---|---|---|---|---|---|---|
| Addressing Mode | Opcode | Length | Speed | ||||
| Stack (Direct Page Indirect) | D4 | 2 bytes | 6 cycles* | ||||
| Flags Affected | ||||||||
|---|---|---|---|---|---|---|---|---|
| N | V | M | X | D | I | Z | C | |
| . | . | . | . | . | . | . | . | |
PEI (Push Effective Indirect address) is a 65c816 instruction that pushes a 16-bit value to the stack. This value need not actually be an address. This value is found at the address formed by adding the operand byte to the direct page register. The high byte (found at the effective address plus one) is pushed first, then the low byte.
No flags are affected.
PEI works even in emulation mode.
Syntax
PEI (dp) PEI dp
Cycle Penalty
- PEI takes one extra cycle if the low byte of the direct page register is nonzero.
See Also
External Links
- Eyes & Lichty, page 474 on PEI
- Labiak, page 158 on PEI
- snes9x implementation of PEI: https://github.com/snes9xgit/snes9x/blob/master/cpuops.cpp#L1658
- undisbeliever on PEI: https://undisbeliever.net/snesdev/65816-opcodes.html#pei-push-effective-indirect-address
- how PEI behaves in emulation mode - section 7.2 of 65c816 datasheet: https://www.westerndesigncenter.com/wdc/documentation/w65c816s.pdf
- Clark, Bruce. http://www.6502.org/tutorials/65c816opcodes.html#6.8.1