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gbdk-2020

GameBoy Development Kit
download: https://git.y1.nz/archives/gbdk.tar.gz
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gbdk-lib/libc/targets/sm83/far_ptr.s

      1 ;--------------------------------------------------------------------------
      2 ;  far_ptr.s
      3 ;
      4 ;  Copyright (C) 2020, Tony Pavlov
      5 ;
      6 ;  This library is free software; you can redistribute it and/or modify it
      7 ;  under the terms of the GNU General Public License as published by the
      8 ;  Free Software Foundation; either version 2, or (at your option) any
      9 ;  later version.
     10 ;
     11 ;  This library is distributed in the hope that it will be useful,
     12 ;  but WITHOUT ANY WARRANTY; without even the implied warranty of
     13 ;  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
     14 ;  GNU General Public License for more details.
     15 ;
     16 ;  You should have received a copy of the GNU General Public License
     17 ;  along with this library; see the file COPYING. If not, write to the
     18 ;  Free Software Foundation, 51 Franklin Street, Fifth Floor, Boston,
     19 ;   MA 02110-1301, USA.
     20 ;
     21 ;  As a special exception, if you link this library with other files,
     22 ;  some of which are compiled with SDCC, to produce an executable,
     23 ;  this library does not by itself cause the resulting executable to
     24 ;  be covered by the GNU General Public License. This exception does
     25 ;  not however invalidate any other reasons why the executable file
     26 ;   might be covered by the GNU General Public License.
     27 ;--------------------------------------------------------------------------
     28 
     29         .module     far_ptr
     30 
     31         .include    "global.s"
     32 
     33         .area   _HOME
     34 
     35 ___call__banked::
     36         ldh A, (#__current_bank)
     37         push AF
     38         ld  HL, #1$
     39         push HL
     40         ld  HL, #___call_banked_addr
     41         ld  A, (HL+)
     42         ld  H, (HL)
     43         ld  L, A
     44         ld  A, (#___call_banked_bank)
     45         ldh (#__current_bank), A
     46         ld  (rROMB0),A
     47         jp  (HL)
     48 1$:
     49         pop AF
     50         ldh (#__current_bank), A
     51         ld  (rROMB0), A
     52         ret
     53 
     54 _to_far_ptr::
     55         ld  a, c
     56         ld  c, e
     57         ld  e, a
     58         ld  a, b
     59         ld  b, d
     60         ld  d, a
     61         ret
     62 
     63         .area  _DATA
     64 
     65 ___call_banked_ptr::
     66 ___call_banked_addr::
     67     .ds 0x02    ; far pointer offset
     68 ___call_banked_bank::
     69     .ds 0x02    ; far pointer segment

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