Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!bloom-beacon!gatech!hubcap!ncrcae!ncr-sd!hp-sdd!hplabs!hpfcdc!rjn
From: rjn@hpfcdc.HP.COM (Bob Niland)
Newsgroups: comp.sys.hp
Subject: Re: IENQAK on HP-UX 2.10 ???
Message-ID: <5570127@hpfcdc.HP.COM>
Date: 26 Feb 89 01:38:11 GMT
References: <16@pttdis.UUCP>
Organization: HP Ft. Collins, Co.
Lines: 37

re: "When trying to use the 'ienqak' mode of the tty driver, I get the
     response: 'unknown mode'."
     
> The manual clearly states that that mode should be available.
> stty(1) and termio(7)

ienqak was only ever supported on Series 500. Series 200 and 300 silently
ignore it.  Series 800 gives an error.  Here is the current manpage text:

     TERMIO(7)			   HP-UX		     TERMIO(7)

 ...

     DEPENDENCIES
	  Series 300

	       The c_iflag field parameter IENQAK (enable output
	       pacing control) is not supported.

	  Series 800
	       The ENQ/ACK protocol and the IENQAK bit are not
	       supported.

> How do I get the driver to answer an ACK on all ENQ's coming in,
> without high CPU loads (by reading on character basis)?

Even if the 800 supported IENQAK, it wouldn't help you, since the HP-UX
(500) implementation was host-mode only, i.e. the host driver would
issue an ENQ and wait for an ACK before sending a block of 80 characters.

All is not lost, however, since ENQ/ACK is a half-duplex protocol, it is
relatively easy to implement in user code.  Have your application perform
input in single-character or raw mode, and look for ENQs.  ACK them.

Regards,                                              Hewlett-Packard
Bob Niland      ARPA: rjn%hpfcrjn@hplabs.HP.COM       3404 East Harmony Road
                UUCP: [hplabs|hpfcse]!hpfcla!rjn      Ft Collins CO 80525-9599