dram-8bit.asm

   1 ; DRAM interface for 2 RAM chips. Supports up to 4 Mbyte of DRAM.
   2 ; This is part of the Z80-CP/M emulator written by Sprite_tm.
   3
   4 ;    Copyright (C) 2010 Leo C.
   5
   6 ;    This file is part of avrcpm.
   7 ;
   8 ;    avrcpm is free software: you can redistribute it and/or modify it
   9 ;    under the terms of the GNU General Public License as published by
  10 ;    the Free Software Foundation, either version 3 of the License, or
  11 ;    (at your option) any later version.
  12 ;
  13 ;    avrcpm is distributed in the hope that it will be useful,
  14 ;    but WITHOUT ANY WARRANTY; without even the implied warranty of
  15 ;    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  16 ;    GNU General Public License for more details.
  17 ;
  18 ;    You should have received a copy of the GNU General Public License
  19 ;    along with avrcpm.  If not, see <http://www.gnu.org/licenses/>.
  20 ;
  21 ;    $Id$
  22 ;
  23
  24         .cseg
  25
  26 ; ------------------ DRAM routines -------------
  27
  28 ;Loads the byte on address xh:xl into temp.
  29 ;must not alter xh:xl
  30
  31 dram_read:
  32         cli                             ;
  33         out     PORTD,xh                ;1
  34         out     PORTC,_RAS0             ;1
  35         out     PORTD,xl                ;1
  36         out     PORTC,_CAS0             ;1
  37         out     DDRD,_0                 ;1
  38         out     PORTC,_OE               ;1
  39         rjmp    PC+1                    ;2
  40         dram_wait DRAM_WAITSTATES       ;
  41         in      temp,PIND               ;1
  42         out     PORTC,_255              ;1
  43         out     DDRD,_255               ;1
  44         sei                             ;
  45         ret
  46
  47
  48
  49 ;Writes the byte in temp to  xh:xl
  50 ;must not alter xh:xl
  51
  52 dram_write:
  53         cli
  54         out     PORTD,xh                ;1
  55         out     PORTC,_RAS0             ;1
  56         out     PORTD,xl                ;1
  57         out     PORTC,_CAS0             ;1
  58         out     PORTD,temp              ;1
  59         out     PORTC,_WE               ;1
  60         out     PORTC,_255              ;1  = 7
  61         sei
  62         ret
  63
  64 ; -------------------------------------------------------------------
  65
  66 dram_readw_pp:
  67         rcall   dram_read
  68         adiw    x,1
  69         push    temp
  70         rcall   dram_read
  71         adiw    x,1
  72         mov     temp2,temp
  73         pop     temp
  74         ret
  75
  76 dram_read_pp:
  77         rcall   dram_read
  78         adiw    x,1
  79         ret
  80
  81 ; -------------------------------------------------------------------
  82
  83 dram_writew_pp:
  84         rcall   dram_write
  85         adiw    x,1
  86         mov     temp,temp2
  87 dram_write_pp:
  88         rcall   dram_write
  89         adiw    x,1
  90         ret
  91
  92
  93 ; -------------------------------------------------------------------
  94 ; vim:set ts=8 noet nowrap
  95