firmware/spminterface.h

   1 /* Name: spminterface.h
   2  * Project: USBaspLoader
   3  * Author: Stephan Baerwolf
   4  * Creation Date: 2012-08-01
   5  * Copyright: (c) 2012 by Stephan Baerwolf
   6  * License: GNU GPL v2 (see License.txt)
   7  */
   8
   9 #ifndef SPMINTERFACE_H_f70ba6adf7624275947e859bdbff0599
  10 #define SPMINTERFACE_H_f70ba6adf7624275947e859bdbff0599
  11
  12 /*
  13  * spminterface.h offers a lightweight interface by inserting
  14  * an small machine-subroutine into the bootsection. (right
  15  * after the interrupt-vector-table)
  16  * This subroutine can be called by normal code in order to
  17  * enable it to program the flash (and depending on BLB11-lockbit
  18  * also the bootsection itself). Since SPM-calls from RWW-sections
  19  * will fail to work. The Routine will be called "bootloader__do_spm".
  20  * Its principle assembler-code is depicted below (real code is a
  21  * little machinedependen).
  22  * Interfaces will be the 8-bit registers r10..r13, for details
  23  * also see below. As also the pageaddress-registes (Z and rampZ)
  24  * are interfaced via different registers, it is possible to call
  25  * this routine via indirect call (icall).
  26  * Traditionally it is also possible to rcall, therefore you can
  27  * define "bootloader__do_spm" for your normal code via defsym at
  28  * linking time.
  29  * Example for an atmega8: "-Wl,--defsym=transfer_point=0x1826"
  30  * (since BOOTLOADER_ADDRESS is 0x1800 and there are
  31  * 2x19 = 38 = 0x26 byte for interrupts)
  32  *
  33
  34 bootloader__do_spm:
  35 ;disable interrupts (if enabled) before calling!
  36 ;you may also want to disable wdt, since this routine may busy-loop
  37 ;==================================================================
  38 ;-->INPUT:
  39 ;spmcr (spmcrval determines SPM action) will be register:       r18
  40 ;MCU dependend RA(MPZ should be transfered within register:     r11
  41 ;lo8(Z) should be transfered within register:                   r12
  42 ;hi8(Z) should be transfered within register:                   r13
  43
  44 ;<-->USED/CHANGED:
  45 ;temp0 will be register:                                        r11
  46 ;temp1 will be register:                                        r12
  47 ;temp2 will be register:                                        r13
  48 ;Z (r31:r30) wil be changed during operation
  49
  50 ;<--OUT:
  51 ;==================================================================
  52
  53 ;load pageaddress (Z) from r13:12 since it may was used for icall
  54 mov     rampZ,  r11
  55 mov     r30,    r12
  56 mov     r31,    r13
  57
  58 waitA:                  ;check for previous SPM complete
  59 in      temp0, SPMCR
  60 sbrc    temp0, SPMEN
  61 rjmp    waitA
  62
  63 out     SPMCR, spmcrval ;SPM timed sequence
  64 spm
  65
  66 waitB:                  ;check for previous SPM complete
  67 in      temp0, SPMCR
  68 sbrc    temp0, SPMEN
  69 rjmp    waitB
  70
  71 ;avoid crash of userapplication
  72 ldi     spmcrval, ((1<<RWWSRE) | (1<<SPMEN))
  73 in      temp0,    SPMCR
  74 sbrc    temp0,    RWWSB
  75 rjmp    waitA
  76
  77 ret
  78
  79 *
  80 */
  81
  82 #include <avr/io.h>
  83 #include <avr/pgmspace.h>
  84
  85 #ifndef BOOTLOADER_ADDRESS
  86 // this header is the interface for user-code
  87
  88
  89
  90
  91 #else /*ifndef BOOTLOADER_ADDRESS*/
  92 // this header is used directly within bootloader_do_spm
  93 #include "bootloaderconfig.h"
  94
  95 #if HAVE_SPMINTEREFACE
  96
  97
  98 /*
  99  * insert architecture dependend "bootloader_do_spm"-code
 100  *
 101  * try to make this array as big as possible
 102  * (so bootloader always uses 2kbytes flash)
 103  */
 104 #if defined (__AVR_ATmega8__) || defined (__AVR_ATmega8HVA__)
 105 //assume  SPMCR==0x37, SPMEN==0x0, RWWSRE=0x4, RWWSB=0x6
 106 const uint16_t bootloader__do_spm[22] PROGMEM = {0x0000, 0x2dec, 0x2dfd, 0xb6b7, 0xfcb0, 0xcffd, 0xbf27, 0x95e8, 0xb6b7,
 107                                                  0xfcb0, 0xcffd, 0xe121, 0xb6b7, 0xfcb6, 0xcff4, 0x9508, 0xFFFF, 0xFFFF,
 108                                                  0xFFFF, 0xFFFF, 0xFFFF, 0xFFFF};
 109 /*
 110 00001826 <bootloader__do_spm>:
 111     1826:       00 00           nop
 112     1828:       ec 2d           mov     r30, r12
 113     182a:       fd 2d           mov     r31, r13
 114
 115 0000182c <waitA>:
 116     182c:       b7 b6           in      r11, 0x37       ; 55
 117     182e:       b0 fc           sbrc    r11, 0
 118     1830:       fd cf           rjmp    .-6             ; 0x182c <waitA>
 119     1832:       27 bf           out     0x37, r18       ; 55
 120     1834:       e8 95           spm
 121
 122 00001836 <waitB>:
 123     1836:       b7 b6           in      r11, 0x37       ; 55
 124     1838:       b0 fc           sbrc    r11, 0
 125     183a:       fd cf           rjmp    .-6             ; 0x1836 <waitB>
 126     183c:       21 e1           ldi     r18, 0x11       ; 17
 127     183e:       b7 b6           in      r11, 0x37       ; 55
 128     1840:       b6 fc           sbrc    r11, 6
 129     1842:       f4 cf           rjmp    .-24            ; 0x182c <waitA>
 130     1844:       08 95           ret
 131 */
 132 #else
 133   #error "bootloader__do_spm has to be adapted, since there is no architecture code, yet"
 134 #endif
 135
 136
 137 #endif
 138 #endif /*ifdef BOOTLOADER_ADDRESS*/
 139
 140 #endif
 141