Program Counter

The Program Counter (PC) keeps track of which instruction is currently executing. On both the 65c816 and S-SMP it is 16 bits wide. The low byte is called PCL and the high byte is called PCH.

If incremented past FFFFh, it wraps around to zero.^{[E&L, page 34]}

The 6502 had 16-bit absolute addressing but only an 8-bit adder, so in emulation mode branches that cross a page boundary incur a one cycle penalty. 65c816 native mode has no such penalty because the full 16-bit adder is used.

See Also

• Program Bank Register
• Stack Pointer
• Super_FX#Program_Counter_(R15)
• BRA
• JMP
• RTS
• RTL

References

• Eyes & Lichty, page 33
• subparagraph 8.1.4 on page 3-8-4 of Book I of the official Super Nintendo development manual
• Pickens, John. http://www.6502.org/tutorials/6502opcodes.html#PC
• Clark, Bruce. http://www.6502.org/tutorials/65c816opcodes.html#6.2.1.1