; demo.psm: PicoBlaze demo (8-bit counter)
; Copyright (C) 2009 Brno University of Technology,
;                    Faculty of Information Technology
; Author(s): Zdenek Vasicek <vasicek AT fit.vutbr.cz>
;
; LICENSE TERMS
;
; Redistribution and use in source and binary forms, with or without
; modification, are permitted provided that the following conditions
; are met:
; 1. Redistributions of source code must retain the above copyright
;    notice, this list of conditions and the following disclaimer.
; 2. Redistributions in binary form must reproduce the above copyright
;    notice, this list of conditions and the following disclaimer in
;    the documentation and/or other materials provided with the
;    distribution.
; 3. All advertising materials mentioning features or use of this software
;    or firmware must display the following acknowledgement:
;
;      This product includes software developed by the University of
;      Technology, Faculty of Information Technology, Brno and its
;      contributors.
;
; 4. Neither the name of the Company nor the names of its contributors
;    may be used to endorse or promote products derived from this
;    software without specific prior written permission.
;
; This software or firmware is provided ``as is'', and any express or implied
; warranties, including, but not limited to, the implied warranties of
; merchantability and fitness for a particular purpose are disclaimed.
; In no event shall the company or contributors be liable for any
; direct, indirect, incidental, special, exemplary, or consequential
; damages (including, but not limited to, procurement of substitute
; goods or services; loss of use, data, or profits; or business
; interruption) however caused and on any theory of liability, whether
; in contract, strict liability, or tort (including negligence or
; otherwise) arising in any way out of the use of this software, even
; if advised of the possibility of such damage.
;
; $Id$
;
;
;-------------------------------------------------------------------------------


CONSTANT port_counter, 80 ; Port address
CONSTANT delay_loop, 5E   ; Loop delay

; =================================================
; Main routine
; =================================================

start: ; Init the value of s7
       LOAD s7, 00

       ; Write the s7 value to port
next:  OUTPUT s7, port_counter
       CALL delay
       ADD s7, 01
       JUMP next

; =================================================
; Delay routine (~1 sec.)
; =================================================
; PicoBlaze requires 2 clocks per instruction
; 1s ~ 25M cycles for fclk = 25 MHz
; 2 + (4 + (4 + 4*256 + 4) * 256 + 4)*delay_loop + 2 = 
; = 4 + 264200*delay_loop
delay:
       LOAD s2, 00
rpt3:  ADD s2, 01

       LOAD s1, 00
rpt2:  ADD s1, 01

       LOAD s0, 00
rpt1:  ADD s0, 01
       JUMP NZ,rpt1

       COMPARE s1, 00
       JUMP NZ,rpt2

       COMPARE s2, delay_loop
       JUMP NZ,rpt3 
      
       RETURN