motorola 68000 cpu quick reference · registers · addressing modes · full instruction set · branch conditions · status register decoder · genesis mega drive dev tool · runs locally
section
registers
D0–D7Data32-bitGeneral-purpose data registers. All sizes (byte/word/long) operate on low 8/16/32 bits. High bits preserved on .B/.W operations.
A0–A6Address32-bitAddress registers. Always hold 32-bit addresses. Word source operands are sign-extended to 32 bits. Flags not affected by MOVEA/ADDA/SUBA/CMPA.
A7 / SPStack32-bitStack pointer. In supervisor mode: SSP (supervisor stack). In user mode: USP. Always word-aligned (even address). Saved by LINK.
PCProgram Counter32-bitProgram counter. Points to next instruction. Used by PC-relative addressing modes.
SRStatus16-bitStatus register: high byte = system byte (T1,T0,S,M,I2-I0); low byte = CCR (X,N,Z,V,C). Only accessible in supervisor mode for full SR; use MOVE.B #n,CCR for user CCR.
USPUser SP32-bitUser stack pointer (not directly accessible in supervisor mode — use MOVE USP,An / MOVE An,USP).