; ***************************************************************************
; copyright   : (C) 2025 by Martin Preuss
; email       : martin@libchipcard.de
;
; ***************************************************************************
; * This file is part of the project "AqHome".                              *
; * Please see toplevel file COPYING of that project for license details.   *
; ***************************************************************************


; ***************************************************************************
; defines



; ***************************************************************************
; data

.dseg

xramLastAddress: .byte 2





; ***************************************************************************
; code

.cseg



; ---------------------------------------------------------------------------
; @routine XRAM_Init @global
;

XRAM_Init:
  clr r16
  sts xramLastAddress, r16
  sts xramLastAddress+1, r16

  inr r16, MCUCR
  sbr r16, (1<<SRE)
  outr MCUCR, r16

  rcall xramWritePattern
  rcall xramVerifyPattern

  ret
; @end


; ---------------------------------------------------------------------------
; @routine XRAM_Fini @global
;

XRAM_Fini:
  ret
; @end



; ---------------------------------------------------------------------------
; @routine xramWritePattern
;
; Write a pattern to memory (high byte of address)

xramWritePattern:
  ldi xl, LOW(RAMEND+1)
  ldi xh, LOW(RAMEND+1)
xramWritePattern_loop:
    mov r16, xh
    st X, r16
    adiw xh:xl, 1
  brne xramWritePattern_loop
  ret
; @end



; ---------------------------------------------------------------------------
; @routine xramVerifyPattern
;
; Write a pattern to memory (high byte of address)

xramVerifyPattern:
  ldi xl, LOW(RAMEND+1)
  ldi xh, LOW(RAMEND+1)
xramVerifyPattern_loop:
    mov r16, xh
    ld r17, X
    cp r16, r17
    brne xramVerifyPattern_end
    adiw xh:xl, 1
  brne xramVerifyPattern_loop
xramVerifyPattern_end:
  sbiw xh:xl, 1
  sts xramLastAddress, xl
  sts xramLastAddress+1, xh
  ret
; @end