Subversion Repositories wb4pb

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;; This sourcecode is released under BSD license.

;; Please see http://www.opensource.org/licenses/bsd-license.php for details!

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;;

;; Copyright (c) 2010, Stefan Fischer 

;; All rights reserved.

;;

;; Redistribution and use in source and binary forms, with or without

;; modification, are permitted provided that the following conditions are met:

;;

;;  * Redistributions of source code must retain the above copyright notice,

;;    this list of conditions and the following disclaimer.

;;  * 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.

;;  * Neither the name of the author nor the names of his contributors may be

;;    used to endorse or promote products derived from this software without

;;    specific prior written permission.

;;

;; THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "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 COPYRIGHT HOLDER OR CONTRIBUTORS BE

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;; filename: pbwbgpio.psm

;; description: gpio example, demonstrating access to wishbone peripherals

;; todo4user: modify main program and gpio_init code as needed

;; version: 0.0.0

;; changelog: - 0.0.0, initial release

;;            - ...

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; IMPORTANT NOTICE!

; be carefull, if using interrupts. wishbone cycles must be atomar, as any

; other processor local bus cycles are normally be. interrupting wishbone

; access may cause a crash of external wishbone master fsm, especially, if

; program flow through isr leads to another wishbone cycle!

NAMEREG sF , wb_addr

NAMEREG sE , wb_data ; also used as tmp-reg for status polling

CONSTANT WB_ACK_FLAG , 01

CONSTANT GPIO_IO_ADDR , 00

CONSTANT GPIO_OE_ADDR , 01

ADDRESS 000

; main entry point

DISABLE INTERRUPT

CALL gpio_init

; mirroring upper nibble gpio inputs

; to lower nibble gpio outputs

LOAD wb_addr , GPIO_IO_ADDR

mainloop:

  CALL wb_rd

  NAMEREG s0 , i

  LOAD i , 04

  for_i_in_4_downto_1_loop: ; bitshifting (wb_data>>4)

    SR0 wb_data

    SUB i , 01

    JUMP NZ , for_i_in_4_downto_1_loop

  CALL wb_wr

  JUMP mainloop

gpio_init:

  ; setting all outputs low

  LOAD wb_addr , GPIO_IO_ADDR

  LOAD wb_data , 00

  CALL wb_wr

  ; configuring lower gpio nibble as output

  LOAD wb_addr , GPIO_OE_ADDR

  LOAD wb_data , 0F

  CALL wb_wr

RETURN

; subroutines wb_wr and wb_rd are working together with external wbm_picoblaze

; wishbone adapter module and therefore should not be modified. wb_wait_on_ack

; is a supporting subroutine, which should not be called directly

;

; transfer principle wishbone write:

; 1. OUTPUT cycle to set up wishbone address, data and control signals from

;    PORT_ID, OUT_PORT and WRITE_STROBE

; 2. INPUT cycle(s) to poll wishbone peripheral acknowledgement using IN_PORT

; => at least one OUTPUT and one INPUT cycle for a write

;

; transfer principle wishbone read:

; 1. INPUT cycle to set up wishbone address and control signals from PORT_ID

;    and READ_STROBE

; 2. INPUT cycle(s) to poll wishbone peripheral acknowledgement using IN_PORT

; 3. the very next INPUT cycle after acknowledgement contains valid wishbone

;    data from IN_PORT

; => at least three INPUT cycles for a read

;

; calling examples:

;

; wishbone write code =>

;

; LOAD wb_addr ,  ; setting up address

; LOAD wb_data ,  ; setting up data

; CALL wb_wr ; starting wishbone write cycle

;  ; wishbone cycle finished

;

; wishbone read code =>

;

; LOAD wb_addr ,  ; setting up address

; CALL wb_rd ; starting wishbone read cycle

;  ; wishbone cycle finished, wb_data is updated now

; wishbone write access

wb_wr:

  OUTPUT wb_data , (wb_addr)

  CALL wb_wait_on_ack

RETURN

; wishbone read access

wb_rd:

  CALL wb_wait_on_ack

  INPUT wb_data , (wb_addr)

RETURN

; waiting on wishbone cycle to complete

wb_wait_on_ack:

  INPUT wb_data , (wb_addr)

  TEST wb_data , WB_ACK_FLAG

  JUMP Z , wb_wait_on_ack

RETURN

; interrupt handling template, if needed

isr:

RETURNI DISABLE

ADDRESS 3FF

JUMP isr