On Tue, 2002-05-21 at 09:51, Robert Davies wrote:
> On Monday 20 May 2002 23:22, you wrote:
> > On Mon, 2002-05-20 at 22:55, Matthew Sackman wrote:
> > > Yep, mine's arrived and is working fine. However, the cable is an
> > > unterminated affair (50 pin IDC). No manual for the tape drive.
> > > There's one jumper on it marked "TP". Does one think that that enables
> > > or disables internal termination or does it have nothing to do with
> > > termination? Any ideas at all?
> >
> > TP Means Terminator Power, I.E. the drive will feed 5 volts to the SCSI
> > bus to power a terminator at the end of the cable. Usually the SCSI
> > controller will put power on the bus, but if you have a long SCSI chain
> > it would probably more appropriate to enable TP on the last drive just
> > before the terminator. There is usually another jumper labelled TE
> > (Terminator Enable) or are there may be sockets for single in-line
> > terminator (resistor) packs.
>
> As far as I understood the terminators provide the correct capacitance, to
> terminate the bus, and active powered ones are preferred as they are more
> accurate and reliable.
>
> To be sure, previous poster would do well to find the SCSI FAQ with google,
> there's a mine of info on various types, and pitfalls.
>
> Rob
I am a trained Electronics Engineer and have 20 years computer
experience and I can assure you that the termination is formed by a
combination of 220ohm and 330ohm resistors connected as a potential
divider between the ground and +5V line, LVD termination consists of a
pull-up resistor only.
David Bottrill
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