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The dmascc_cfg utility
======================
Use this utility to configure the dmascc driver.
Usage:
------
dmascc_cfg <interface> [ options ... ]
Options:
--------
--show Show all configurable parameters for this port.
May be specified at any time by any user.
All other options change parameters and thus may only be specified by root
and only when the interface is down.
f ... floating-point argument, i ... integer argument.
--frequency f Set frequency of baud rate generator. A value of 0 disables
the baud rate generator and the digital PLL. Use the
--show option to check whether the frequency you selected
could be approximated with sufficient accuracy.
--nrzi 0 | 1 0 selects NRZ mode, 1 selects NRZI mode.
--clocks i Set clock mode. You may OR together three choices (other
values are not supported and may cause strange results):
TX clock pin: 0x00 input
0x05 output TX clock *
0x06 output baud rate generator *
0x07 output digital PLL *
TX clock source: 0x00 RX clock pin
0x08 TX clock pin #
0x10 baud rate generator
0x18 digital PLL +
RX clock source: 0x00 RX clock pin
0x20 TX clock pin
0x40 baud rate generator
0x60 digital PLL +
* Not allowed on PI2 Port A if J3 is installed.
# TX clock pin must be configured as input
+ The BRG frequency must be equal to 32 times the baud rate.
--txdelay f Set the transmit delay (in ms).
--txpause f Set the delay (in ms) between two transmitted packets.
This parameter sometimes helps to reduce RX FIFO overruns,
if the receiving station has a slower CPU than the
transmitting station and cannot re-initialize the SCC's
receiver quickly enough.
--txtimeout f Set the time (in ms), after which the transmitter may
not squeeze in another packet, but rather has to go
off-air.
--txtail f Set the time (in ms) between the end of the last packet
and the RTS line actually going inactive.
--rtsoff f Set the DCD settling time (in ms) after switching off the
transmitter. During this period the DCD line is being
ignored. This parameter is especially useful for the
S5SCC/DMA, which frequently generates short DCD pulses
after switching from TX to RX.
--dcdon f Set the DCD settling time (in ms) after the DCD line has
become active. This parameter should be < txdelay.
--dcdoff f Set the DCD settling time (in ms) after the DCD line has
become inactive. This parameter should be >= rtsoff.
--slottime f Set the slot time (in ms).
--persist i Set the persistence parameter (1 <= i <= 256). After the
DCD off settling time has expired, the driver waits
random(0..255)/persist*slottime before activating the
RTS line. Integer arithmetic is being performed;
persist==256 thus means zero delay in any case (which only
makes sense in a two-station scenario).
--waittime f Set the minimum time (in ms) before a station may start
transmitting again (after the RTS off settling time has
expired). This value should be larger than
255/persist*slottime.
--dma i Set the DMA channel (-1, 0, 1, or 3). -1 disables DMA.
0 is only valid on the S5SCC/DMA. Remember, DMA can be
used only on channel A (dmascc0, dmascc2, and so on).
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