1 | /*****************************************************************************/ |
2 | /* */ |
3 | /* memory.h */ |
4 | /* */ |
5 | /* Memory subsystem for the 6502 simulator */ |
6 | /* */ |
7 | /* */ |
8 | /* */ |
9 | /* (C) 2002-2012, Ullrich von Bassewitz */ |
10 | /* Roemerstrasse 52 */ |
11 | /* D-70794 Filderstadt */ |
12 | /* EMail: uz@cc65.org */ |
13 | /* */ |
14 | /* */ |
15 | /* This software is provided 'as-is', without any expressed or implied */ |
16 | /* warranty. In no event will the authors be held liable for any damages */ |
17 | /* arising from the use of this software. */ |
18 | /* */ |
19 | /* Permission is granted to anyone to use this software for any purpose, */ |
20 | /* including commercial applications, and to alter it and redistribute it */ |
21 | /* freely, subject to the following restrictions: */ |
22 | /* */ |
23 | /* 1. The origin of this software must not be misrepresented; you must not */ |
24 | /* claim that you wrote the original software. If you use this software */ |
25 | /* in a product, an acknowledgment in the product documentation would be */ |
26 | /* appreciated but is not required. */ |
27 | /* 2. Altered source versions must be plainly marked as such, and must not */ |
28 | /* be misrepresented as being the original software. */ |
29 | /* 3. This notice may not be removed or altered from any source */ |
30 | /* distribution. */ |
31 | /* */ |
32 | /*****************************************************************************/ |
33 | |
34 | |
35 | |
36 | #include <string.h> |
37 | |
38 | #include "memory.h" |
39 | |
40 | |
41 | |
42 | /*****************************************************************************/ |
43 | /* Data */ |
44 | /*****************************************************************************/ |
45 | |
46 | |
47 | |
48 | /* THE memory */ |
49 | static unsigned char Mem[0x10000]; |
50 | |
51 | |
52 | |
53 | /*****************************************************************************/ |
54 | /* Code */ |
55 | /*****************************************************************************/ |
56 | |
57 | |
58 | |
59 | void MemWriteByte (unsigned Addr, unsigned char Val) |
60 | /* Write a byte to a memory location */ |
61 | { |
62 | Mem[Addr] = Val; |
63 | } |
64 | |
65 | |
66 | |
67 | void MemWriteWord (unsigned Addr, unsigned Val) |
68 | /* Write a word to a memory location */ |
69 | { |
70 | MemWriteByte (Addr, Val & 0xFF); |
71 | MemWriteByte (Addr + 1, Val >> 8); |
72 | } |
73 | |
74 | |
75 | |
76 | unsigned char MemReadByte (unsigned Addr) |
77 | /* Read a byte from a memory location */ |
78 | { |
79 | return Mem[Addr]; |
80 | } |
81 | |
82 | |
83 | |
84 | unsigned MemReadWord (unsigned Addr) |
85 | /* Read a word from a memory location */ |
86 | { |
87 | unsigned W = MemReadByte (Addr++); |
88 | return (W | (MemReadByte (Addr) << 8)); |
89 | } |
90 | |
91 | |
92 | |
93 | unsigned MemReadZPWord (unsigned char Addr) |
94 | /* Read a word from the zero page. This function differs from MemReadWord in that |
95 | ** the read will always be in the zero page, even in case of an address |
96 | ** overflow. |
97 | */ |
98 | { |
99 | unsigned W = MemReadByte (Addr++); |
100 | return (W | (MemReadByte (Addr) << 8)); |
101 | } |
102 | |
103 | |
104 | |
105 | void MemInit (void) |
106 | /* Initialize the memory subsystem */ |
107 | { |
108 | /* Fill memory with illegal opcode */ |
109 | memset (Mem, 0xFF, sizeof (Mem)); |
110 | } |
111 | |