From ff94ea93e254f7ee8c91e42a3a783f5b2262a391 Mon Sep 17 00:00:00 2001
From: Christian Pointner <equinox@spreadspace.org>
Date: Sun, 7 Jul 2013 00:18:05 +0000
Subject: skipping 'invalid' code doesn't work on some hardware droping this
 feature

git-svn-id: https://svn.spreadspace.org/pic/trunk@45 a09c6847-51d9-44de-8ef2-e725cf50f3c7
---
 bootloader/bootloader.asm | 28 ++++++++++++----------------
 downloader/proto.txt      |  8 +++++---
 2 files changed, 17 insertions(+), 19 deletions(-)

diff --git a/bootloader/bootloader.asm b/bootloader/bootloader.asm
index dc7d119..f8b609c 100644
--- a/bootloader/bootloader.asm
+++ b/bootloader/bootloader.asm
@@ -37,7 +37,7 @@ VERSION_MAJ     EQU       .0
 VERSION_MIN     EQU       .1
 DEVID_H         EQU       H'20'
 DEVID_L         EQU       H'82'
-FSS             EQU       .8
+FSS             EQU       .16
 MESS_H          EQU       .0
 MESS_L          EQU       .64
 SUPPORTED_H     EQU       .0
@@ -348,7 +348,7 @@ cmd_w_config
   ;;  actual flash/eeprom functions
   ;; flash read --------
 read_flash_segment
-  movlw     FSS
+  movlw     FSS                 ; initialize EEADR:EEADRH and FSR
   movwf     cnt1
   movlw     b'01011000'
   movwf     STATUS
@@ -360,19 +360,19 @@ read_flash_segment
   movf      INDF,w
   movwf     EEADRH
 read_flash_segment_loop
-  bsf       STATUS,RP0
+  bsf       STATUS,RP0          ; perform the actual read
   bsf       EECON1,EEPGD
   bsf       EECON1,RD
   nop
   nop
   bcf       STATUS,RP0
-  movf      EEDAT,w
+  movf      EEDAT,w             ; load code word from EEDAT:EEDATH to combuff
   movwf     INDF
   incf      FSR,f
   movf      EEDATH,w
   movwf     INDF
   incf      FSR,f
-  incfsz    EEADR,f
+  incfsz    EEADR,f             ; increment flash address
   goto      read_flash_segment_next
   incf      EEADRH,f
 read_flash_segment_next
@@ -404,17 +404,8 @@ write_flash_segment_loop
   movf      INDF,w
   movwf     EEDATH
 
-  bsf       STATUS,RP0          ; if code word is 0xFFFF, read the current value first
-  btfss     INDF,7              ; this will leave this word unchanged
-  goto      write_flash_segment_write
-
+  bsf       STATUS,RP0          ; now start the acutal write sequence
   bsf       EECON1,EEPGD
-  bsf       EECON1,RD
-  nop
-  nop
-
-write_flash_segment_write
-  bsf       EECON1,EEPGD        ; now start the acutal write sequence
   bsf       EECON1,WREN
   movlw     H'55'
   movwf     EECON2
@@ -431,8 +422,13 @@ write_flash_segment_write
 write_flash_segment_next
   decfsz    cnt1,f
   goto      write_flash_segment_loop
+  bsf       STATUS,RP0
+  clrw
+  btfsc     EECON1,WRERR
+  movlw     E_FLASH_WERR
   bcf       STATUS,RP1
-  clrf      combuff + .1  ; = E_OK
+  bcf       STATUS,RP0
+  movwf     combuff + .1  ; = E_OK
   retlw     .2            ; bytes to send
 
   ;; -------------------------------------
diff --git a/downloader/proto.txt b/downloader/proto.txt
index f4f32c8..e85368e 100644
--- a/downloader/proto.txt
+++ b/downloader/proto.txt
@@ -60,8 +60,8 @@ identify:
       fss:
          1byte, flash segment size
          The number of words of one flash segment which has to be written at once.
-         The downloader can fill up holes by supplying the illegal code word 0xFFFF
-         for some addresses. The bootloader will skip those areas.
+         If less than <fss> should be updated the downloader has to perform a read
+         operation first.
 
       mess:
          2bytes, maximum eeprom segment size
@@ -133,7 +133,9 @@ write flash:
     5 | <ret> | <csum>
 
   The bootloader writes <data> (which has to contain exactly <fss> words) to address
-  <addr> inside the flash.
+  <addr> inside the flash. The start address has to be aligned to <fss> boundaries.
+  Before writing the memory region will be erased. If there are words which shouldn't
+  be altered the downloader has to read these words first and reprogram the whole segment.
 
 
 read eeprom:
-- 
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