pdp11v/usr/man/a_man/man7/du.7

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.TH DU 7 "PDP-11 only"
.SH NAME
du \- \s-1DU-11\s0 synchronous line interface
.SH DESCRIPTION
The files
.BR du0 ,
.BR du1 ,
etc.,
represent interfaces to synchronous modems
such as the
Bell System
200-series
synchronous
.SM DATA-PHONE\*S\*R
sets.
.I Read\^
and
.I write\^
calls
to
.B du?
are unlimited, but work best when restricted to less than 512 bytes.
Each
.I write\^
call is sent as a single record.
Seven bits from each byte
are written, along with an eighth, odd-parity,
bit.
The ``sync'' characters must be supplied by the user.
Each
.I read\^
call returns the characters read from a
single record.
Seven bits are returned unaltered; the eighth bit
is set if the byte was not received in odd parity.
An error is returned if
.I "data-set ready\^"
is not present.
.SH FILES
/dev/du?
.SH "SEE ALSO"
acu(7).
.\"	@(#)du.7	5.2 of 5/18/82