;;
  ;;  spreadspace pic utils
  ;;
  ;;
  ;;  Copyright (C) 2011 Christian Pointner <equinox@spreadspace.org>
  ;;                         
  ;;  This file is part of spreadspace pic utils.
  ;;
  ;;  spreadspace pic utils is free software: 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
  ;;  any later version.
  ;;
  ;;  spreadspace pic utils is distributed in the hope that it will be useful,
  ;;  but WITHOUT ANY WARRANTY; without even the implied warranty of
  ;;  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  ;;  GNU General Public License for more details.
  ;;
  ;;  You should have received a copy of the GNU General Public License
  ;;  along with spreadspace pic utils. If not, see <http://www.gnu.org/licenses/>.
  ;;
  ;; -------------------------------------
  ;; PREAMBLE

  LIST      p=16F1847
  include   "p16f1847.inc"
  __config  _CONFIG1,  _FOSC_INTOSC & _WDTE_OFF & _PWRTE_OFF & _MCLRE_ON & _CP_OFF & _CPD_OFF & _BOREN_OFF & _CLKOUTEN_OFF & _IESO_OFF & _FCMEN_OFF
  __config  _CONFIG2,  _WRT_OFF & _PLLEN_OFF & _STVREN_OFF & _BORV_LO & _LVP_OFF


  ;; -------------------------------------
  ;; DEFINES
  ;; constants
BUF_STARTH    EQU 020h
BUF_STARTL    EQU 000h
BUF_ENDH      EQU 023h
BUF_ENDL      EQU 0BFh

  ;; I/O Pins
;; PortA
C1m           EQU .0
C2p           EQU .1
AMP_OUT       EQU .2
ADC_IN        EQU .3
CCP4          EQU .4
;; PortB
SDI           EQU .1
SDO           EQU .2
INT           EQU .3
SCK           EQU .4
CS            EQU .5
FILTER_EN     EQU .7

  ;; variables
  ;;  all Pages
CNT0          EQU H'0070'
CNT1          EQU H'0071'
CNT2          EQU H'0072'
TMP           EQU H'0073'

FLAGS         EQU H'007F'

    ;; bits
;; FLAGS
UNDERRUN      EQU .0
OVERRUN       EQU .1
  
  ;; -------------------------------------
  ;; OFFSET
  org	      .0
  goto      init

  ;; -------------------------------------
  ;; Interrupts
  org       .4
  movlb     b'00000000'
  btfsc     PIR1,SSP1IF
  goto      int_spi
  retfie

int_spi
  bsf       PORTA,7
  bcf       PIR1,SSP1IF
  movlb     b'00000100'
  movf      SSP1BUF,w
  incf      TMP,f
  movf      TMP,w
  movwf     SSP1BUF
  movlb     b'00000000'
  bcf       PORTA,7
  retfie

  ;; -------------------------------------
  ;; SUBROUTINES
wbuf_reset
  movlw     BUF_STARTH
  movwf     FSR0H
  movlw     BUF_STARTL
  movwf     FSR0L
  bcf       FLAGS,OVERRUN
  return

  ;; -------------------
wbuf_next
  btfsc     FLAGS,UNDERRUN
  goto      wbuf_move_ptr

  movf      FSR1H,w
  xorwf     FSR0H,w
  btfss     STATUS,Z
  goto      wbuf_move_ptr

  movf      FSR1L,w
  xorwf     FSR0L,w
  btfss     STATUS,Z
  goto      wbuf_move_ptr

  bsf       FLAGS,OVERRUN
  return

wbuf_move_ptr
  bcf       FLAGS,UNDERRUN
  addfsr    FSR0,1

  movf      FSR0H,w
  sublw     BUF_ENDH
  btfss     STATUS,C
  goto      wbuf_wraparound
  btfss     STATUS,Z
  return
  movf      FSR0L,w
  sublw     BUF_ENDL
  btfsc     STATUS,C
  return

wbuf_wraparound
  movlw     BUF_STARTH
  movwf     FSR0H
  movlw     BUF_STARTL
  movwf     FSR0L
  return


  ;; -------------------
rbuf_reset
  movlw     BUF_STARTH
  movwf     FSR1H
  movlw     BUF_STARTL
  movwf     FSR1L
  bsf       FLAGS,UNDERRUN

  ;; -------------------
rbuf_next
  btfsc     FLAGS,OVERRUN
  goto      rbuf_move_ptr

  movf      FSR0H,w
  xorwf     FSR1H,w
  btfss     STATUS,Z
  goto      rbuf_move_ptr

  movf      FSR0L,w
  xorwf     FSR1L,w
  btfss     STATUS,Z
  goto      rbuf_move_ptr

  bsf       FLAGS,UNDERRUN
  return

rbuf_move_ptr
  bcf       FLAGS,OVERRUN
  addfsr    FSR1,1

  movf      FSR1H,w
  sublw     BUF_ENDH
  btfss     STATUS,C
  goto      rbuf_wraparound
  btfss     STATUS,Z
  return
  movf      FSR1L,w
  sublw     BUF_ENDL
  btfsc     STATUS,C
  return

rbuf_wraparound
  movlw     BUF_STARTH
  movwf     FSR1H
  movlw     BUF_STARTL
  movwf     FSR1L
  return

  ;; -------------------------------------
  ;; INIT
init
  ;; BANK 4
  movlb     b'00000100'
  movlw     b'01000000'
  movwf     SSP1STAT
  movlw     b'00010000'
  movwf     SSP1CON3
  movlw     b'00100100'
  movwf     SSP1CON1
  
  ;; BANK 3
  movlb     b'00000011'
  clrf      ANSELA
  clrf      ANSELB

  ;; BANK 2
  movlb     b'00000010'

  ;; BANK 1
  movlb     b'00000001'
  movlw     b'01111111'
  movwf     TRISA
  movlw     b'01110011'
  movwf     TRISB
;  movlw     b'01011000'                 ;  1 MHz
;  movlw     b'01100000'                 ;  2 MHz
  movlw     b'01101000'                 ;  4 MHz
;  movlw     b'01110000'                 ;  8 MHz
;  movlw     b'01111000'                 ; 16 MHz
  movwf     OSCCON
  movlw     b'00001000'
  movwf     PIE1
  
  ;; BANK 0
  movlb     b'00000000'
  clrf      PIR1
  movlw     b'11000000'
  movwf     INTCON
  bcf       PORTA,7

  bcf       PORTB,3

  

  ;; -------------------------------------
  ;; MAINLOOP
main
;;   movlw     .255
;;   movwf     CNT0

;; outer1
;;   movlw     .255
;;   movwf     CNT1

;; outer
;;   movlw     .20
;;   movwf     CNT2
  
;; inner
;;   decfsz    CNT2,f
;;   goto      inner
  
;;   decfsz    CNT1,f
;;   goto      outer

;;   decfsz    CNT0,f
;;   goto      outer1

;;   movlw     b'00001000'
;;   xorwf     PORTB,f

  goto	    main

  ;; -------------------------------------
  ;; END
  end