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Improve -B bitclock documentation

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Stefan Rueger
2022-10-23 22:26:07 +01:00
parent 2c7083f001
commit 16922842be
3 changed files with 32 additions and 26 deletions
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src/doc/avrdude.texi
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@@ -440,19 +440,21 @@ Override the RS-232 connection baud rate specified in the respective
programmer's entry of the configuration file.
@item -B @var{bitclock}
Specify the bit clock period for the JTAG interface or the ISP clock (JTAG ICE only).
The value is a floating-point number in microseconds.
Alternatively, the value might be suffixed with "Hz", "kHz", or "MHz",
in order to specify the bit clock frequency, rather than a period.
The default value of the JTAG ICE results in about 1 microsecond bit
clock period, suitable for target MCUs running at 4 MHz clock and
above.
Unlike certain parameters in the STK500, the JTAG ICE resets all its
parameters to default values when the programming software signs
off from the ICE, so for MCUs running at lower clock speeds, this
parameter must be specified on the command-line.
It can also be set in the configuration file by using the 'default_bitclock'
keyword.
Specify the bit clock period for the JTAG, PDI, TPI, UPDI, or ISP
interface. The value is a floating-point number in microseconds.
Alternatively, the value might be suffixed with "Hz", "kHz" or
"MHz" in order to specify the bit clock frequency rather than a
period. Some programmers default their bit clock value to a 1
microsecond bit clock period, suitable for target MCUs running at 4
MHz clock and above. Slower MCUs need a correspondingly higher bit
clock period. Some programmers reset their bit clock value to the
default value when the programming software signs off, whilst
others store the last used bit clock value. It is recommended to
always specify the bit clock if read/write speed is important. You
can use the 'default_bitclock' keyword in your
@code{~/.config/avrdude/avrdude.rc} or @code{~/.avrduderc}
configuration file to assign a default value to keep from having to
specify this option on every invocation.
@item -c @var{programmer-id}
Specify the programmer to be used. AVRDUDE knows about several common