SCSI TermPwr jumper

[Hodgkinson]

Hi,
I’m currently setting up a SCSI HDD for use with the Squirrel SCSI interface.

On most drives there's a jumper labelled TermPwr:

Open: TermPwr for on-board terminators provided from SCSI connector, pin 26. Drive TermPwr is not connected to SCSI connector pin 26.
Shorted: TermPwr for on-board terminators provided by the drive, and drive TermPwr is connected to SCSI connector pin 26.

At the moment I've set the jumper open in order to reduce the chance of destroying anything else that might be providing power to this rail.
For an external active terminator to work, does at least one of the drives in the chain have to provide power onto this pin? Or are external terminators self-powered?
Similarly, does the Squirrel already provide power onto this pin, or, if the last drive on the chain is internally terminated, would the TermPwr have to be turned on one of the drives in the chain?

[Hodgkinson]

Thanks for the info!

I'll probably try the drive (Which has an internal jumperable terminator too) without the TP set, and I'll see if the LED on the active terminator that I have lights up or not. If not, I’ll set the TP jumper and try again.

Cheers,
Hodgkinson.

[Hodgkinson]

It would seem that the SquirrelSCSI does in fact provide its own termpwr rail output. With the termpwr jumper on the HDD open (Disabled) and an external terminator plugged into the drive, the terminator will only light up and the drive will only spin up when the A1200 is turned on.
With the drives' termpwr jumper closed (Enabled), the terminator will light up and the drive spin up irrespective of whether the A1200 is connected or not.

Related question: Suppose I upgrade from the SquirrelSCSI, to, say a Blizzard SCSI kit for my 1230IV, would I still be able to access the drives and their associated data?

Thanks,
Hodgkinson.

[Hodgkinson]

Thanks  ;-)