hdh —
ACC IF-11/HDH IMP network interface
pseudo-device imp
hdh0 at uba0 csr 166740 vector hdhintr
NOTE: This driver has not been ported from 4.4BSD yet.
NOTE: At the moment, NetBSD does not
    support IMP, so this manual page is not relevant.
The 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
    imp(4). The configuration
    entry for the IMP must also include the pseudo-device as
    shown above in the SYNOPSIS.
  - hdh%d: not alive.
- The initialization routine was entered even though the device did not
      autoconfigure. This indicates a system problem.
- 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.
- hdh%d: LINE UP.
- This indicates that both the HDLC and HDH protocols have declared the link
      to the IMP alive.
- hdh%d: LINE DOWN.
- This indicates that the link to the IMP has died.
- hdh%d: TIMEOUT.
- hdh%d: HOST DATA ERROR.
- hdh%d: IMP SEQUENCE ERROR.
- hdh%d: HOST SEQUENCE ERROR.
- These errors indicate that an HDH protocol error has been detected.
- hdh%d: cannot get supervisor cmnd buffer.
- This error indicates that an mbuf could not be allocated
      to send a command to the IF-11/HDH.
Any other error message from hdh%d: indicates a serious error
    detected by either the driver or the IF-11/HDH firmware.
The hdh driver appeared in
  4.3BSD.