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Describe how to disable the DWEN fuse. 

git-svn-id: svn://svn.savannah.nongnu.org/avrdude/trunk/avrdude@651 81a1dc3b-b13d-400b-aceb-764788c761c2
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Joerg Wunsch 2006-09-07 20:42:01 +00:00
parent 9a961e3054
commit a41fdc3385
3 changed files with 80 additions and 1 deletions
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@ -1,3 +1,8 @@
2006-09-07 Joerg Wunsch <j@uriah.heep.sax.de>
* avrdude.1: Describe how to disable the DWEN fuse.
* doc/avrdude.texi: (Ditto.)
2006-09-07 Joerg Wunsch <j@uriah.heep.sax.de>
* jtagmkII.c: Translate numerical response codes to strings.

26
avrdude.1
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@ -676,7 +676,31 @@ library
Schematic of programming hardware
.El
.\" .Sh EXAMPLES
.\" .Sh DIAGNOSTICS
.Sh DIAGNOSTICS
.Bd -literal
avrdude: jtagmkII_setparm(): bad response to set parameter command: RSP_FAILED
avrdude: jtagmkII_getsync(): ISP activation failed, trying debugWire
avrdude: Target prepared for ISP, signed off.
avrdude: Please restart avrdude without power-cycling the target.
.Ed
.Pp
If the target AVR has been set up for debugWire mode (i. e. the
.Em DWEN
fuse is programmed), normal ISP connection attempts will fail as
the
.Em /RESET
pin is not available.
When using the JTAG ICE mkII in ISP mode, the message shown indicates
that
.Nm
has guessed this condition, and tried to initiate a debugWire reset
to the target.
When successful, this will leave the target AVR in a state where it
can respond to normal ISP communication again (until the next power
cycle).
Typically, the same command is going to be retried again immediately
afterwards, and will then succeed connecting to the target using
normal ISP communication.
.Sh SEE ALSO
.Xr avr-objcopy 1 ,
.Xr ppi 4 ,

50
doc/avrdude.texi
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@ -1938,6 +1938,56 @@ In order to successfully program the EEPROM that way, a prior chip
erase (with the EESAVE fuse unprogrammed) is required.
This also applies to the STK500 in high-voltage programming mode.
@item
Problem: How do I turn off the @var{DWEN} fuse?
Solution: If the @var{DWEN} (debugWire enable) fuse is activated,
the @var{/RESET} pin is not functional anymore, so normal ISP
communication cannot be established.
There are two options to deactivate that fuse again: high-voltage
programming, or getting the JTAG ICE mkII talk debugWire, and
prepare the target AVR to accept normal ISP communication again.
The first option requires a programmer that is capable of high-voltage
programming (either serial or parallel, depending on the AVR device),
for example the STK500. In high-voltage programming mode, the
@var{/RESET} pin is activated initially using a 12 V pulse (thus the
name @emph{high voltage}), so the target AVR can subsequently be
reprogrammed, and the @var{DWEN} fuse can be cleared. Typically, this
operation cannot be performed while the AVR is located in the target
circuit though.
The second option requires a JTAG ICE mkII that can talk the debugWire
protocol. The ICE needs to be connected to the target using the
JTAG-to-ISP adapter, so the JTAG ICE mkII can be used as a debugWire
initiator as well as an ISP programmer. AVRDUDE will then be activated
using the @var{jtag2isp} programmer type. The initial ISP
communication attempt will fail, but AVRDUDE then tries to iniate a
debugWire reset. When successful, this will leave the target AVR in a
state where it can accept standard ISP communication. The ICE is then
signed off (which will make it signing off from the USB as well), so
AVRDUDE has to be called again afterwards. This time, standard ISP
communication can work, so the @var{DWEN} fuse can be cleared.
The pin mapping for the JTAG-to-ISP adapter is:
@table @code
@item JTAG pin
ISP pin
@item 1
@code{3}
@item 2
@code{6}
@item 3
@code{1}
@item 4
@code{2}
@item 6
@code{5}
@item 9
@code{4}
@end table
@end itemize