2.9BSD/usr/man/cat4/du.4

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DU(4)               UNIX Programmer's Manual                DU(4)

NAME
     du, dp - DU-11/DUP-11 201 data-phone interface

DESCRIPTION
     The _d_p_0 file is a 201 data-phone interface.  _R_e_a_d and _w_r_i_t_e
     calls to dp0 are limited to a maximum of 512 bytes.  Each
     _w_r_i_t_e call is sent as a single record.  Seven bits from each
     byte are written along with an eighth odd parity bit.  The
     sync must be user supplied.  Each _r_e_a_d call returns charac-
     ters received from a single record.  Seven bits are returned
     unaltered; the eighth bit is set if the byte was not
     received in odd parity.  A 10 second time out is set and a
     zero-byte record is returned if nothing is received in that
     time.

FILES
     /dev/dp0

SEE ALSO
     dn(4)

DIAGNOSTICS
     _E_r_r_n_o is set to ENXIO if an _o_p_e_n(2) fails because the device
     is already in use by another process.

BUGS
     The name _d_p_0 is a historical dreg.

Printed 7/31/83                                                 1