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.\"	@(#)hdh.4	6.3 (Berkeley) 6/23/90
.\"
.TH HDH 4 "June 23, 1990"
.UC 6
.SH NAME
hdh \- ACC IF-11/HDH IMP interface
.SH SYNOPSIS
.B "pseudo-device imp"
.br
.B "device hdh0 at uba0 csr 166740 vector hdhintr"
.SH DESCRIPTION
The 
.I hdh
device provides an HDLC Host (HDH)
interface to an IMP.  It is normally used when participating
in the DARPA Internet.  The controller itself is not accessible
to users, but instead provides the hardware support to the IMP
interface described in
.IR imp (4).
When configuring, the 
.I imp
pseudo-device must also be included.
.SH DIAGNOSTICS
.BR "hdh%d: not alive" .
The initialization routine was entered even though the device
did not autoconfigure.  This indicates a system problem.
.PP
.BR "hdh%d: cannot get chan %d uba resources" .
Insufficient UNIBUS resources existed to initialize the device.
This is likely to be a shortage of UNIBUS mapping registers.
.PP
.BR "hdh%d: LINE UP" .
This indicates that both the HDLC and HDH protocols have declared the
link to the IMP alive.
.PP
.BR "hdh%d: LINE DOWN" .
This indicates that the link to the IMP has died.
.PP
.BR "hdh%d: HOST SEQUENCE ERROR"
.br
.BR "hdh%d: IMP SEQUENCE ERROR"
.br
.BR "hdh%d: HOST DATA ERROR"
.br
.BR "hdh%d: TIMEOUT"
.br
These errors indicate that an HDH protocol error has been detected.
.PP
.BR "hdh%d: cannot get supervisor cmnd buffer" .
This error indicates that an
.I mbuf
could not be allocated to send a command to the IF-11/HDH.
.PP
Any other error message from hdh%d: indicates a serious error
detected by either the driver or the IF-11/HDH firmware.
.SH "SEE ALSO"
netintro(4)