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fuse.h
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1 /* Copyright (c) 2007, Atmel Corporation
2 All rights reserved.
3
4 Redistribution and use in source and binary forms, with or without
5 modification, are permitted provided that the following conditions are met:
6
7 * Redistributions of source code must retain the above copyright
8 notice, this list of conditions and the following disclaimer.
9
10 * Redistributions in binary form must reproduce the above copyright
11 notice, this list of conditions and the following disclaimer in
12 the documentation and/or other materials provided with the
13 distribution.
14
15 * Neither the name of the copyright holders nor the names of
16 contributors may be used to endorse or promote products derived
17 from this software without specific prior written permission.
18
19 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
20 AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
21 IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
22 ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
23 LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
24 CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
25 SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
26 INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
27 CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
28 ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
29 POSSIBILITY OF SUCH DAMAGE. */
30
31 /* $Id: fuse.h 2107 2010-03-20 18:00:47Z arcanum $ */
32
33 /* avr/fuse.h - Fuse API */
34
35 #ifndef _AVR_FUSE_H_
36 #define _AVR_FUSE_H_ 1
37
38 /* This file must be explicitly included by <avr/io.h>. */
39 #if !defined(_AVR_IO_H_)
40 #error "You must #include <avr/io.h> and not <avr/fuse.h> by itself."
41 #endif
42
43
44 /** \file */
45 /** \defgroup avr_fuse <avr/fuse.h>: Fuse Support
46
47 \par Introduction
48
49 The Fuse API allows a user to specify the fuse settings for the specific
50 AVR device they are compiling for. These fuse settings will be placed
51 in a special section in the ELF output file, after linking.
52
53 Programming tools can take advantage of the fuse information embedded in
54 the ELF file, by extracting this information and determining if the fuses
55 need to be programmed before programming the Flash and EEPROM memories.
56 This also allows a single ELF file to contain all the
57 information needed to program an AVR.
58
59 To use the Fuse API, include the <avr/io.h> header file, which in turn
60 automatically includes the individual I/O header file and the <avr/fuse.h>
61 file. These other two files provides everything necessary to set the AVR
62 fuses.
63
64 \par Fuse API
65
66 Each I/O header file must define the FUSE_MEMORY_SIZE macro which is
67 defined to the number of fuse bytes that exist in the AVR device.
68
69 A new type, __fuse_t, is defined as a structure. The number of fields in
70 this structure are determined by the number of fuse bytes in the
71 FUSE_MEMORY_SIZE macro.
72
73 If FUSE_MEMORY_SIZE == 1, there is only a single field: byte, of type
74 unsigned char.
75
76 If FUSE_MEMORY_SIZE == 2, there are two fields: low, and high, of type
77 unsigned char.
78
79 If FUSE_MEMORY_SIZE == 3, there are three fields: low, high, and extended,
80 of type unsigned char.
81
82 If FUSE_MEMORY_SIZE > 3, there is a single field: byte, which is an array
83 of unsigned char with the size of the array being FUSE_MEMORY_SIZE.
84
85 A convenience macro, FUSEMEM, is defined as a GCC attribute for a
86 custom-named section of ".fuse".
87
88 A convenience macro, FUSES, is defined that declares a variable, __fuse, of
89 type __fuse_t with the attribute defined by FUSEMEM. This variable
90 allows the end user to easily set the fuse data.
91
92 \note If a device-specific I/O header file has previously defined FUSEMEM,
93 then FUSEMEM is not redefined. If a device-specific I/O header file has
94 previously defined FUSES, then FUSES is not redefined.
95
96 Each AVR device I/O header file has a set of defined macros which specify the
97 actual fuse bits available on that device. The AVR fuses have inverted
98 values, logical 1 for an unprogrammed (disabled) bit and logical 0 for a
99 programmed (enabled) bit. The defined macros for each individual fuse
100 bit represent this in their definition by a bit-wise inversion of a mask.
101 For example, the FUSE_EESAVE fuse in the ATmega128 is defined as:
102 \code
103 #define FUSE_EESAVE ~_BV(3)
104 \endcode
105 \note The _BV macro creates a bit mask from a bit number. It is then
106 inverted to represent logical values for a fuse memory byte.
107
108 To combine the fuse bits macros together to represent a whole fuse byte,
109 use the bitwise AND operator, like so:
110 \code
111 (FUSE_BOOTSZ0 & FUSE_BOOTSZ1 & FUSE_EESAVE & FUSE_SPIEN & FUSE_JTAGEN)
112 \endcode
113
114 Each device I/O header file also defines macros that provide default values
115 for each fuse byte that is available. LFUSE_DEFAULT is defined for a Low
116 Fuse byte. HFUSE_DEFAULT is defined for a High Fuse byte. EFUSE_DEFAULT
117 is defined for an Extended Fuse byte.
118
119 If FUSE_MEMORY_SIZE > 3, then the I/O header file defines macros that
120 provide default values for each fuse byte like so:
121 FUSE0_DEFAULT
122 FUSE1_DEFAULT
123 FUSE2_DEFAULT
124 FUSE3_DEFAULT
125 FUSE4_DEFAULT
126 ....
127
128 \par API Usage Example
129
130 Putting all of this together is easy. Using C99's designated initializers:
131
132 \code
133 #include <avr/io.h>
134
135 FUSES =
136 {
137 .low = LFUSE_DEFAULT,
138 .high = (FUSE_BOOTSZ0 & FUSE_BOOTSZ1 & FUSE_EESAVE & FUSE_SPIEN & FUSE_JTAGEN),
139 .extended = EFUSE_DEFAULT,
140 };
141
142 int main(void)
143 {
144 return 0;
145 }
146 \endcode
147
148 Or, using the variable directly instead of the FUSES macro,
149
150 \code
151 #include <avr/io.h>
152
153 __fuse_t __fuse __attribute__((section (".fuse"))) =
154 {
155 .low = LFUSE_DEFAULT,
156 .high = (FUSE_BOOTSZ0 & FUSE_BOOTSZ1 & FUSE_EESAVE & FUSE_SPIEN & FUSE_JTAGEN),
157 .extended = EFUSE_DEFAULT,
158 };
159
160 int main(void)
161 {
162 return 0;
163 }
164 \endcode
165
166 If you are compiling in C++, you cannot use the designated intializers so
167 you must do:
168
169 \code
170 #include <avr/io.h>
171
172 FUSES =
173 {
174 LFUSE_DEFAULT, // .low
175 (FUSE_BOOTSZ0 & FUSE_BOOTSZ1 & FUSE_EESAVE & FUSE_SPIEN & FUSE_JTAGEN), // .high
176 EFUSE_DEFAULT, // .extended
177 };
178
179 int main(void)
180 {
181 return 0;
182 }
183 \endcode
184
185
186 However there are a number of caveats that you need to be aware of to
187 use this API properly.
188
189 Be sure to include <avr/io.h> to get all of the definitions for the API.
190 The FUSES macro defines a global variable to store the fuse data. This
191 variable is assigned to its own linker section. Assign the desired fuse
192 values immediately in the variable initialization.
193
194 The .fuse section in the ELF file will get its values from the initial
195 variable assignment ONLY. This means that you can NOT assign values to
196 this variable in functions and the new values will not be put into the
197 ELF .fuse section.
198
199 The global variable is declared in the FUSES macro has two leading
200 underscores, which means that it is reserved for the "implementation",
201 meaning the library, so it will not conflict with a user-named variable.
202
203 You must initialize ALL fields in the __fuse_t structure. This is because
204 the fuse bits in all bytes default to a logical 1, meaning unprogrammed.
205 Normal uninitialized data defaults to all locgial zeros. So it is vital that
206 all fuse bytes are initialized, even with default data. If they are not,
207 then the fuse bits may not programmed to the desired settings.
208
209 Be sure to have the -mmcu=<em>device</em> flag in your compile command line and
210 your linker command line to have the correct device selected and to have
211 the correct I/O header file included when you include <avr/io.h>.
212
213 You can print out the contents of the .fuse section in the ELF file by
214 using this command line:
215 \code
216 avr-objdump -s -j .fuse <ELF file>
217 \endcode
218 The section contents shows the address on the left, then the data going from
219 lower address to a higher address, left to right.
220
221 */
222
223 #ifndef __ASSEMBLER__
224
225 #ifndef FUSEMEM
226 #define FUSEMEM __attribute__((section (".fuse")))
227 #endif
228
229 #if FUSE_MEMORY_SIZE > 3
230
231 typedef struct
232 {
233 unsigned char byte[FUSE_MEMORY_SIZE];
234 } __fuse_t;
235
236
237 #elif FUSE_MEMORY_SIZE == 3
238
239 typedef struct
240 {
241 unsigned char low;
242 unsigned char high;
243 unsigned char extended;
244 } __fuse_t;
245
246 #elif FUSE_MEMORY_SIZE == 2
247
248 typedef struct
249 {
250 unsigned char low;
251 unsigned char high;
252 } __fuse_t;
253
254 #elif FUSE_MEMORY_SIZE == 1
255
256 typedef struct
257 {
258 unsigned char byte;
259 } __fuse_t;
260
261 #endif
262
263 #if !defined(FUSES)
264 #if defined(__AVR_XMEGA__)
265 #define FUSES NVM_FUSES_t __fuse FUSEMEM
266 #else
267 #define FUSES __fuse_t __fuse FUSEMEM
268 #endif
269 #endif
270
271
272 #endif /* !__ASSEMBLER__ */
273
274 #endif /* _AVR_FUSE_H_ */

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