[8185] in linux-scsi channel archive
Re: HP 35470A term power
daemon@ATHENA.MIT.EDU (Kurt Garloff)
Wed Feb 23 12:43:18 2000
Date: Wed, 23 Feb 2000 17:44:41 +0100
From: Kurt Garloff <garloff@suse.de>
To: michael <blindman@voicenet.com>
Cc: linux-scsi@vger.rutgers.edu
Message-ID: <20000223174441.L3231@mobil.tue.nl>
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In-Reply-To: <38B43D5E.5BCB4077@voicenet.com>; from blindman@voicenet.com on Wed, Feb 23, 2000 at 03:04:46PM -0500
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On Wed, Feb 23, 2000 at 03:04:46PM -0500, michael wrote:
> i have a HP 35470A 4mm DAT tape unit. i read at HP.com
> that these units are set to terminate automatically, right?
Hmmm? You don't set a switch, jumper, ... or use a terminator in
connector-shape, but?
* have the HP always terminate the bus? This is broken!
* have the HP autodetect whether it's the last device and in that case
terminate the bus? This is nice, but not unlikely to break, sometimes.
See auto-termination warnings of some controllers ...
> device on the scsi card. i haven't found any solid info on how
> this unit can set or unset internal termination, if at all.
If it's an external device:
Are there two SCSI connectors? If there is only one, the devcice must
terminate the bus anyway, as it can only be the last. Otherwise it
shouldn't.
For internal devices, you really should have a jumper!
> another question with that would be, if it is set to terminate,
> then i don't know if i should use the "term power" with the adaptec
> aha152x card and/or the aha1542 card.
Acc. to SCSI-II, every controller should put power onto the TermPower line
and protect this output line by a diode. That's save by design. Older
(SCSI-I) controllers failed to do that, sometimes, and that's why it's
configurable for some controllers. I don't know about your Adaptecs.
> i have two of these
> dats and have been trying to get them to work with both cards.
> i can load the drivers,
> ( by $insmod aha1542 aha1542=0x330 )
> rewind, but no luck getting them to write and then read back
> without errors. this is the first time i've played with dat on linux.
> the cables work with hdd's and cdroms. i have two cables, they are
> both about 20 inches. one has only one connection, the other has two.
>
> each dat is the last and only device on the cable. set to ID2.
>
> if they are not terminated, and i can't set it intenally - how
> would i terminate it when it's the only device on the chain? is
> there a terminator that attaches to internal ribbon cables? is
> there different kinds, which one to get? ie active, passive?
They exist. I've seen some. If you can get active terminators, go for them.
They are much better and required, if you want to go beyond 5MHz.
> also, should i enable or disable parity?
Enable, unless one of your devices is completely broken.
That way, you have some sort of error detection (with 50% chance to see them
for single errors, sigh!)
> the jumpers on the bottem are are set to what HP defines as
> common for PC's, all on except #3 dip.
You have docu on the jumpers? And there is none for termination.
Call HP! They should tell you ...
> i have also tried a few other combinations using a table found at
> ANDATACO's web site.
Regards,
--
Kurt Garloff <garloff@suse.de> Eindhoven, NL
GPG key: See mail header, key servers Linux kernel development
SuSE GmbH, Nuernberg, FRG SCSI, Security
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