Subversion Repositories zipcpu

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;

; Filename:     wdt.S

;

; Project:      Zip CPU -- a small, lightweight, RISC CPU soft core

;

; Purpose:      Test to see whether or not the watchdog timer works.  We'll

;               start the watchdog, clear a register, then write as many times

;               as we can to memory before the watchdog kicks in.

;

; Creator:      Dan Gisselquist, Ph.D.

;               Gisselquist Tecnology, LLC

;

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;

; 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

;

;

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;

; Registers:

;       R12     Peripheral base

;       R11     Address of our one memory variable

;

#include "sys.i"

start:

        LDI     0xc0000000,R12  ; Get the address of our peripheral base

        MOV     $1(PC),R11      ; Get a memory address for a variable

        BRA     skip_test_variable

test_variable:

        .DAT    0

skip_test_variable:

        LDI     $-1,R0  ; Start the watchdog timer

        STO     R0,sys.bus.wdt(R12)

        LSR     $1,R0   ; R0 now = 0x7fffffff

        STO     R0,sys.bus.tma(R12)

        LSR     $1,R0   ; R0 now = 0x3fffffff

        STO     R0,sys.bus.tmb(R12)

        LSR     $1,R0

        STO     R0,sys.bus.tmc(R12)

        ;

        CLR     R0

wdt_test_loop:

        ADD     $1,R0

        LOD     (R11),R1

        CMP     R0,R1

        STO.LT  R0,(R11)

        TST     -1,R0

        BLT     wdt_test_program_is_broken

        BRA     wdt_test_loop

wdt_test_program_is_broken:

        HALT