• Please review our updated Terms and Rules here

Dual Tandon TM100-1A Configuration for Model 1

A

Avia

Experienced Member
Joined
Jan 17, 2016
Messages
194
Location
Saint Augustine, FL
Hi All,

I am trying to get a dual floppy setup going with my Model 1 using Tandon TM100-1A drives. According to the TRSDOS & Disk Basic Manual, which of course only gives guidance on utilizing the Radio Shack drives 26-1160 (Drive 0) and 26-1161 (Drive 1), the 1160 should have the terminating resistor installed and should be the final drive on the cable.

Would it be the same for the Tandon drives? I wanted to confirm the jumper(photo area 1)/terminator (area 2) settings to be certain I get them right for each drive.

Thanks as always!

Cary

20160728_181656.jpg
 
Yes, the general rule is that there be a terminator on the most distant drive of the chain. Even the IBM PC follows this rule.

In practice, the physical distance is so short between the two drives that either (but not both) can have the terminator. But a terminator is necessary because the floppy bus is an open-collector affair and needs some sort of pullup to +5 somewhere.
 
Thanks for the quick reply Chuck. So I have a terminator on drive 0 and the dip switch to DS0 (dip #2). I have no terminator on drive 1 and the dip switch set to DS1 (dip #3). Drive 0 is the most distant drive in the chain (second connector from the EI - the last two drive connectors are empty) per the TRSDOS Disk basic manual.

A picture is shown below.

However, on boot, drive 0 spins up (no light) for a few seconds and then shuts off. There does not appear to be any drive head activity, and no boot from the disk. I know the drives to be good. When I disconnect Drive 1, and plug drive 0 into the connector closest to the EI, it boots fine.

20160728_193812d.jpg
 
Last edited:
The Original Radio Shack minifloppy disk drive cable has pins pulled from the connectors so Drive 0 will only work when it's plugged into the correct connector. The correct connector/location for drive 0 is the closest drive connector to the Expansion Interface. So, it's no wonder that Drive 0 did not boot from the most distant drive connect, that was the wrong connector.
 
Am I misinterpreting the guidance form the TRSDOS manual?

"If you have two drives, connect 26-1161 to the FIRST connector and 26-1160 to the SECOND connector..."

Pages from TRSDOS_v2.jpg
 
Are you using a fully pinned cable to the drives or the radio shack cable with the pin pulls? I think If using the RS cable you need to enable all drive selects on both drives the cable then selects which drive is 0 or 1. Then try connecting the drives like Microcomputersolutions suggested 0 closest to the EI and 1 at the end and maybe terminate drive 1 then.
 
In addition to the Drive Selects all being jumpered & the farthest drive from the EI having the terminator, the drives have to be setup properly for the TRS-80. Frank Durda's website has info on the jumper settings for the TRS-80s vs IBMs. There is a Disk Change signal among others that the IBMs use and the TRS-80s don't.

Tom
 
TM100's (48 tpi) don't have a disk change signal TM100-1 Documentation. Perhaps you're thinking of a different drive.

In fact, the 5150 and 5160 controllers don't use "Disk Changed" either--that didn't come in until the 5170--and was used on the 1.2M 5.25" drives. Later, 3.5" HD drives incorporated it.
 
You must log in or register to reply here.
Back
Top