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.TH UART 3
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.SH NAME
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uart, eia \- serial communication control
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.SH SYNOPSIS
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.nf
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.B bind -a #t /dev
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.B /dev/eia0
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.B /dev/eia0ctl
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.B /dev/eia0status
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.B /dev/eia1
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.B /dev/eia1ctl
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.B /dev/eia1status
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\&...
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.fi
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.SH DESCRIPTION
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.PP
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The serial line devices serve a one-level directory,
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giving access to the serial ports.
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Device
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.I n
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is accessed through
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.BI eia n
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(the data file),
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.BI eia n ctl
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(the control file), and
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.BI eia n status
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(the read-only status file).
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Reads of the data file will block until at least one byte is available.
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The
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control file
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configures the port.
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It accepts the following commands:
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.TP
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.BI b n
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Set the baud rate to
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.IR n .
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.TP
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.BI c n
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Set hangup on DCD if
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.I n
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is non-zero; else clear it.
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.TP
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.BI d n
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Set DTR if
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.I n
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is non-zero;
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else clear it.
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.TP
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.BI e n
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Set hangup on DSR if
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.I n
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is non-zero; else clear it.
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.TP
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.B f
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Flush output queue.
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.TP
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.B h
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Close input and output queues.
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.TP
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.BI i n
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Enable/disable the FIFOs.
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If
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.I n
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is zero the FIFOs are disabled;
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otherwise
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.I n
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is taken as a trigger level for the FIFOs.
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The trigger levels supported are device dependant,
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but usually include 1, 4 and 8.
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An unrecognised,
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but non-zero,
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value of
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.I n
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causes the maximum-supported trigger level to be set.
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.TP
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.BI k n
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Send a break lasting
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.I n
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milliseconds.
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.TP
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.BI l n
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Set number of bits per byte to
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.IR n .
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Legal values are 5, 6, 7, or 8.
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.TP
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.BI m n
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Obey modem CTS signal if
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.I n
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is non-zero;
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else clear it.
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.TP
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.B n
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Make writes non-blocking.
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.TP
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.BI p c
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Set parity to odd if
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.I c
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is
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.BR o ,
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to even if
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.I c
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is
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.BR e ;
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else set no parity.
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.TP
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.BI q n
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Set input and output queue limits to
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.IR n .
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.TP
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.BI r n
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Set RTS if
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.I n
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is non-zero;
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else clear it.
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.TP
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.BI s n
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Set number of stop bits to
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.IR n .
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Legal values are 1 or 2.
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.TP
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.BI w n
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Set the uart clock timer to
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n times 100us.
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.IP
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.PP
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The status
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files contain a textual representation of the status of the line, in the format of the
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commands used on the
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control
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file.
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.SH SOURCE
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.B /sys/src/9/port/devuart.c
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.br
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.B /sys/src/9/*/uart*.c