risc lfsr shifter

        BRA main
main    LDR R3, SEED
        MOV R0, R3
loop    JMS LFSRSh
        OUT R0
        CMP R0, R3
        BNE loop
        HLT
LFSRSh  MOV R1, R0
        AND R1, #1
        LSR R0, #1
        CMP R1, #1
        BEQ xorit
        RET
xorit   LDR R2, MASK
        XOR R0, R2
        RET
MASK    DAT 12
SEED    DAT 15