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Simple PCIe FMC carrier SPEC - Software
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Simple PCIe FMC carrier SPEC - Software
Commits
37ecaba6
Commit
37ecaba6
authored
Oct 16, 2013
by
Benoit Rat
Committed by
Alessandro Rubini
Feb 14, 2014
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doc: update doc with new P/p, C/c mode
parent
e0e8e29c
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spec-sw.in
doc/spec-sw.in
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doc/spec-sw.in
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37ecaba6
...
...
@@ -1008,23 +1008,55 @@ The current version of the tool supports the following commands:
Configure one or more channels for the specified mode. Each mode
is represented by one character; the latter form above thus
configures all 5 channels by means of a since 5-bytes-long string.
Supported modes are ``@code
{
I
}
'' (input),
``@code
{
0
}
'' and ``@code
{
1
}
'' (output, steady state),
``@code
{
D
}
'' (DIO core output) or ``@code
{
-
}
'' (unchanged).
configures all 5 channels by means of a 5-bytes-long string,
each characters specifies a mode according to the next table.
@end table
This is the list of supported modes for channels:
@table @code
@item I i
Input mode, with termination or without termination. Uppercase
forces the termination on (the rationale is you need a stronger
signal to drive the input). Termination is 50 Ohm. Pulses on
an input channel are timestamped.
@item C c
``Clock'' input. This mode (with or without termination) is
used to feed a clock to the White Rabbit core (currently the
WR core supports a 10MHz input on channel 4 (the last one).
For other channel, the mode is just like @t
{
I
}
or @t
{
i
}
but
without timestamping (and thus without a software interrupt).
@item 0 1
Digital output mode, from the GPIO logic core, resp. low and high.
Both modes disable the termination resistor.
@item D d
DIO core output (not the GPIO core). With this mode the channel
is driven by the WR-aware digital I/O, and can thus generate pulses
and so on. Uppercase enables the termination.
A channel managed by the DIO core is normally low and can
pulse high on request (see @code
{
pulse
}
command. Uppercase @code
{
D
}
or @code
{
I
}
activate the 50-ohm termination
resistor with either WR-DIO or input mode,
while lowercase @code
{
d
}
or @code
{
i
}
disable the termination.
Currently output modes are always without termination,
but I may add @code
{
L
}
and
@code
{
H
}
if needed: the hardware supports all combinations).
Please note that the @code
{
pulse
}
command turns the affected channel in
@i
{
DIO
}
mode anyways (without changing the termination).
command. The termination resistor doesn't make much sense for
output, but the code is provided for consistency with input modes.
@item P p
Pulse per second output from the White Rabbit core. This
@i
{
pps
}
is sharper in its absolute time than the one that can be
generated by software using DIO pulses. Again, upper case
selects the termination, for symmetry with input modes.
@end table
Generation of a pulse train is performed by
software running at interrupt time,
because the @i
{
simple DIO
}
card and gateware can only emit a single pulse at
...
...
@@ -1100,6 +1132,11 @@ and the @i{simple-DIO} mezzanine card, this package includes
@file
{
wr
-
dio
-
pps
}
, which features a very small and readable source
file.
The program is meant as a source code example, more than a real PPS
signal. If you need a real WR
-
driven pulse
-
per
-
second, you should
configure the channel accordingly, with ``@t
{
wr
-
dio
-
cmd mode <ch>
p
}
''.
The program just fires a
1
ms
-
long @i
{
pps
}
pulse on one of the output
channels. The device name defaults to @i
{
wr
0
}
but can specify a different one;
the channel number is a mandatory argument.
...
...
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