X-Git-Url: https://review.openocd.org/gitweb?a=blobdiff_plain;f=doc%2Fopenocd.texi;h=bb96a2e63e2bcd0966c80a17ef474935417f2fb1;hb=43483e5054c78e0fdfaebed5e14c14246af07c97;hp=475482df9c92d5a1dcdc6117f52aa5a920a35b00;hpb=61af6a681671eae69256dcc5b9e853cf9b161387;p=openocd.git

diff --git a/doc/openocd.texi b/doc/openocd.texi
index 475482df9c..bb96a2e63e 100644
--- a/doc/openocd.texi
+++ b/doc/openocd.texi
@@ -1975,6 +1975,42 @@ When using PPDEV to access the parallel port, use the number of the parallel por
 you may encounter a problem.
 @end deffn
 
+@deffn Command {parport_toggling_time} [nanoseconds]
+Displays how many nanoseconds the hardware needs to toggle TCK;
+the parport driver uses this value to obey the
+@command{jtag_khz} configuration.
+When the optional @var{nanoseconds} parameter is given,
+that setting is changed before displaying the current value.
+
+The default setting should work reasonably well on commodity PC hardware.
+However, you may want to calibrate for your specific hardware.
+@quotation Tip
+To measure the toggling time with a logic analyzer or a digital storage
+oscilloscope, follow the procedure below:
+@example
+> parport_toggling_time 1000
+> jtag_khz 500
+@end example
+This sets the maximum JTAG clock speed of the hardware, but
+the actual speed probably deviates from the requested 500 kHz.
+Now, measure the time between the two closest spaced TCK transitions.
+You can use @command{runtest 1000} or something similar to generate a
+large set of samples.
+Update the setting to match your measurement:
+@example
+> parport_toggling_time <measured nanoseconds>
+@end example
+Now the clock speed will be a better match for @command{jtag_khz rate}
+commands given in OpenOCD scripts and event handlers.
+
+You can do something similar with many digital multimeters, but note
+that you'll probably need to run the clock continuously for several
+seconds before it decides what clock rate to show.  Adjust the
+toggling time up or down until the measured clock rate is a good
+match for the jtag_khz rate you specified; be conservative.
+@end quotation
+@end deffn
+
 @deffn {Config Command} {parport_write_on_exit} (on|off)
 This will configure the parallel driver to write a known
 cable-specific value to the parallel interface on exiting OpenOCD
@@ -5259,11 +5295,23 @@ Several of the parameters must reflect the trace port capabilities,
 which are a function of silicon capabilties (exposed later
 using @command{etm info}) and of what hardware is connected to
 that port (such as an external pod, or ETB).
-The @var{width} must be either 4, 8, or 16.
-The @var{mode} must be @option{normal}, @option{multiplexted},
-or @option{demultiplexted}.
+The @var{width} must be either 4, 8, or 16,
+except with ETMv3.0 and newer modules which may also
+support 1, 2, 24, 32, 48, and 64 bit widths.
+(With those versions, @command{etm info} also shows whether
+the selected port width and mode are supported.)
+
+The @var{mode} must be @option{normal}, @option{multiplexed},
+or @option{demultiplexed}.
 The @var{clocking} must be @option{half} or @option{full}.
 
+@quotation Warning
+With ETMv3.0 and newer, the bits set with the @var{mode} and
+@var{clocking} parameters both control the mode.
+This modified mode does not map to the values supported by
+previous ETM modules, so this syntax is subject to change.
+@end quotation
+
 @quotation Note
 You can see the ETM registers using the @command{reg} command.
 Not all possible registers are present in every ETM.