gbdk-2020 | GameBoy Development Kit |
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gbdk-lib/libc/asm/z80/__sdcc_critical.s
1 ;--------------------------------------------------------------------------
2 ; __sdcc_critical.s
3 ;
4 ; Copyright (C) 2020, Sergey Belyashov
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 .area _CODE
30
31 .globl ___sdcc_critical_enter
32 ;
33 ; NMOS Z80 compatible
34 ; this function cannot be placed at 0x0000...0x00ff addresses
35 ;
36 ___sdcc_critical_enter::
37 xor a, a
38 push af
39 pop af
40 ld a, i
41 di
42 ret pe ;enabled interrupts
43 dec sp
44 dec sp
45 pop af
46 or a, a ;A = 0 if interrupts disabled
47 jr NZ, 00100$
48 ;inetrrupts disabled
49 sub a, a ;force P/V = 0
50 ret
51 ;interrupts enabled
52 00100$:
53 xor a, a ;force P/V = 1
54 ret
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