Stack

The Stack is a buffer which remembers the state of subroutines that are currently executing.

On the 65c816, the stack is always in bank zero.^[3] It can be thousands of bytes deep.^[1]

In emulation mode it wraps within page one.^[2]

The stack grows towards zero, but the most recently pushed byte is nontheless called the top of the stack.^[4] These instructions push things to the stack:

• PEA
• PEI
• PER
• PHA
• PHB
• PHD
• PHK
• PHP
• PHX
• PHY
• JSR
• JSL
• COP
• BRK

PL* instructions take one cycle more than their PH* counterparts. These instructions pull things from the stack:

• PLA
• PLB
• PLD
• PLP
• PLX
• PLY
• RTS
• RTL
• RTI

Note the lack of PLK. PHS and PLS similarly do not exist, nor do any instructions performing the inverse of PEA, PEI, or PER.

See Also

• Stack Pointer

References

1. Wilson, Garth. https://wilsonminesco.com/816myths
2. Clark, Bruce. http://www.6502.org/tutorials/65c816opcodes.html#5.1.1
3. section 2.11 of 65c816 datasheet: https://www.westerndesigncenter.com/wdc/documentation/w65c816s.pdf
4. Eyes & Lichty, page 33