TPDD
Tandy Portable Disk Drive
There were two versions of the original Tandy Portable Disk Drive, "26-3808 Tandy Portable Disk Drive" or now called "TPDD1", and "26-3814 Tandy Portable Disk Drive 2" or "TPDD2". Both were very similar.
The original TPDD1 is a re-branded Brother FB100. In fact the Brother FB100 was sold under several names. At least:
- Brother FB100
- TANDY Portable Disk Drive
- knitking FDD19
- Purple Computing D103
The TPDD2 was also sold under multiple names. At least:
- TANDY Portable Disk Drive 2
- XOB Disc-88
Common features of both versions
- Size, shape, weight
- Batteris: 4 x AA
- Wall power: 5.5mm x 2.1mm, 6vdc, center negative, 400ma (Tandy 26-3804)
- Media: 3.5" DD, aka "720K" diskettes (not HD 1.44M)
- Drive is single-sided. The disks may be single or double-sided, but the drive only uses one side.
Documentation
Tandy Portable Disk Drive
100K
- File:TPDD1 ROM.zip - dump of the 4k rom built into the HD63A01V1 cpu
- ROM is also identical in Brother FB-100, KnitKing FDD19, and Purple Computing D103
Tandy Portable Disk Drive 2
200K, in the form of 2 100K banks
- File:TPDD2 ROM.zip - dump of the 4k rom built into the HD63A01V1 cpu
Parts
Belt
Standard size code: FRW-8.5
Search "FRW 8.5 belt" on Google or ebay
Cable
The "RS-232C" interface to the TPDD is actually 5v TTL (0v to +5v), while RS-232 serial ports use -12v to +12v. So the cable isn't just a cable, it has electronics inside the DB25 plug to convert the signal levels between TTL and RS-232.
You can't buy the original special cable any more, but you can build one, or buy one from ArcadeShopper (picture is outdated, the cables are the same as the one on github), or SoiGeneris.
Pinout
+------------------------------------------------+ | | | | | RS-232C | | ___ | | +--+ +--+ +-----+ | | | 7 5 3 1 | | (o) | | | | 8 6 4 2 | | | | | +---------+ +-----+ | +------------------------------------------------+
- 1 GND
- 2 CTS
- 3 DTR
- 4 RTS
- 5 DSR
- 6 TXD
- 7 RXD
- 8 EB+ (External Battery +4.8 to +6v) (Only on TPDD2, n/c on TPDD1)
Software
Software related to these drives can be broken into 2 main categories, clients and servers.
A TPDD client (aka dos) is software that uses a TPDD drive. This includes TS-DOS, and the program called "Floppy" which came on the special disk that came with the TANDY versions of the drives.
A TPDD server (aka emulator) is software that pretends to BE a TPDD drive. This includes LaddieAlpha, dl2, and others.
Misc Related Info
Low-profile DIP switch that fits under the cover on the bottom, which can be installed on Brother FB-100, KnitKing FDD19, or Purple Computing D103 to give access to all possible drive operation modes like TPDD1.
https://www.digikey.com/en/products/detail/cui-devices/DS04-254-2L-04BK/11310925
TS-DOS implements an extension to the TPDD protocol to provide subdirectories.
A real TPDD or TPDD2 doesn't support this, but some TPDD emulators do (NADSBOX, LaddieAlpha, dl2, PDDuino, at least)
TPDD uses standard 720k DD 3.5" disks, but uses a format that is incompatible with modern pc drive controllers.
Normal MS-DOS formatted disks are written with MFM encoding, while the TPDD uses FM encoding.
Even using special software to read non-standard track/sector formats, you can't make a normal drive & drive controller read or write FM. An old pc with an early floppy controller chip and an old 720k drive may be able to do it.
To read or write a TPDD disk from a modern machine, you need a working TPDD drive, the special RS232-to-TTL level-shifting serial cable, a 9F-to-25F straight through (not null-modem) serial adapter or combination of cables & adapters, and TPDD client software to talk to the drive over the serial connection the same way the M100 does. See pdd.sh, PDD.EXE, or TpddTool.py from the TPDD clients link above.
Don't use 1.44M HD disks in a TPDD. Use 720K DD disks.
