URL:
<http://savannah.nongnu.org/bugs/?38192>
Summary: eeprom_update_byte does not use bitwise AND
Project: AVR C Runtime Library
Submitted by: None
Submitted on: Tue 29 Jan 2013 11:23:56 AM UTC
Category: Library
Severity: 3 - Normal
Priority: 5 - Normal
Item Group: libc code
Status: None
Percent Complete: 0%
Assigned to: None
Originator Email: popo...@oko.fei.tuke.sk
Open/Closed: Open
Discussion Lock: Any
Release: Any
Fixed Release: None
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Details:
As described in AVR103, there is no need of erase cycle if new value match
bitwise AND between the old value and the new value.
Patch below uses this functionality, eeprom endurance is higher and update
time is reduced too.
% diff -u eeupd_byte.S.orig eeupd_byte.S
--- eeupd_byte.S.orig 2013-01-29 10:54:43.000000000 +0100
+++ eeupd_byte.S 2013-01-29 12:02:25.000000000 +0100
@@ -88,8 +88,14 @@
breq 2f
# if defined (EEPM0) && defined (EEPM1)
- ; Set programming mode: erase and write.
+ ; Set programming mode: write only
out _SFR_IO_ADDR (EECR), __zero_reg__
+ sbi _SFR_IO_ADDR (EECR),EEPM1
+ ;test bitwise AND
+ and __tmp_reg__, r18
+ cpse __tmp_reg__, r18
+ ; final value different, set programing mode: erase and write
+ cbi _SFR_IO_ADDR (EECR),EEPM1
# elif defined (EEPM0) || defined (EEPM1)
# error /* Unknown EECR register. */
# endif
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