Subversion Repositories xulalx25soc

////////////////////////////////////////////////////////////////////////////////
//
// Filename:    genlrs.S
//
// Project:     XuLA2 board
//
// Purpose:     
//
//
// Creator:     Dan Gisselquist, Ph.D.
//              Gisselquist Technology, LLC
//
////////////////////////////////////////////////////////////////////////////////
//
// Copyright (C) 2015, Gisselquist Technology, LLC
//
// This program is free software (firmware): you can redistribute it and/or
// modify it under the terms of  the GNU General Public License as published
// by the Free Software Foundation, either version 3 of the License, or (at
// your option) any later version.
//
// This program is distributed in the hope that it will be useful, but WITHOUT
// ANY WARRANTY; without even the implied warranty of MERCHANTIBILITY or
// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
// for more details.
//
// License:     GPL, v3, as defined and found on www.gnu.org,
//              http://www.gnu.org/licenses/gpl.html
//
//
////////////////////////////////////////////////////////////////////////////////
//
//
entry:
        ;                               ; R0 -- used by test_lrs
        ;                               ; R1 -- used by test_lrs
        ;                               ; R2 -- used by test_lrs
        ;                               ; R3 = return address
        LDI     0x80000000,R4           ; Taps
        LDI     0x00800000,R6           ; Current Memory Address
        MOV     R6,R7                   ; Start of memory
        LDI     0x00ffffff,R8           ; End of memory
        
test_next_lrs:
        MOV     __HERE__+2(PC),R3
        BRA     test_lrs
        CMP     0,R0
        BGE     next_tap_set
        STO     R0,(R6)
        ADD     1,R6
        AND     R8,R6
        OR      R7,R6
next_tap_set:
        ADD     1,R4
        BNZ     test_next_lrs
        HALT

test_lrs:
        ; R0 = taps on entry
        ; R0 = length on return
        ; R3 = return PC address
        CLR     R1      ;       R1 will be our length
        LDI     1,R2    ;       R2 will be our fill
test_lrs_loop:
        LSR     1,R2
        XOR.C   R0,R2
        ADD     1,R1
        CMP     1,R2
        BNZ     test_lrs_loop
        MOV     R1,R0

        MOV     R3,PC