Micropolis Futuredata floppy controller
Bipolar PROM reader adapter

Most recent revision of this page, dated Dec 18 2015, copyright 2015 Herb Johnson. Links and intro updated Feb 05 2016.

Background: I have an interest in floppy controllers before the Intel and Western Digital single-chip floppy controller chip sets were created. Micropolis made a number of non-FDC-chip floppy controllers in the mid-1970's. This page discusses one of them, board number 100119, marked "Futuredata". Thanks to Al Kossow for calling my attention to the Micropolis board on this page. It used 82S181 biploar PROMS, not supported on most PROM writers. So I wired-up an IC socket, to enable my PROM programmer to read (not program) that device. Likewise, another person wired-up an IC socket, to read Harris 7641 bipolar 512x8 proms, from an old microcomputer product. Details of both adapters are included.

I'm also interested in old bipolar PROMS, which were used in those early controllers. For more information about bipolar fusable PROMS in vintage computers, check this linked Web page where I show several examples and how-to-read and program them. - herb Johnson

Micropolis controller

[micropolis futuredata]
Here's an image of a Micropolis board number 100119, marked "Futuredata". Al Kossow called this board set to my attention when he requested information. There's a fair amount of Futuredata information and photos available, on the "bitsavers.org" Web site's Futuredata PDF documentation section. Look in the model 2300 section.

There's a cable from one of the board's connectors to another PC board. That board, 10145A, appears to be used as a wiring adapter only. The Micropolis/Futuredata board supports a 34-pin connector to 5.25-inch floppy drives. The 10145A converts the lines to a 40-pin connector for 8-inch floppy drives.

This image of J1 shows the data interface to the Micropolis card.Here's a power cable to the apparent power connector J4.

This is the front of the 10145A board and this is the back. It appears all the red wires of the power cable are tied together.

82S181 PROMs

The 10019 board has three 82S181 PROMs, which are fuse-link PROMs. They are identified from the corner toward the Z80 CPU as 80007-03-1B; 80007-03-3B; 80007-03-5B. The PCB has an inked number, 9015102. Also in the photo is my DIP socket wired as a PROM reader adapter (see below).

The 82S181 PROM has the same pinout(almost) as some 2716 UV EPROMs. But the 82S181 is a 5-volt only device; some 2716's use -5V as well. The Thompson brand ET2716 is a 5-volt only device. But two of the four chip-select lines to the 82S181 are different on the ET2716.

[micropolis PROM & adapter]
Here's a little text note on how to wire a DIP socket to adapt an 82S181 to be read like a ET2716. the resulting hex file is half 0FFh's, half programmed data. The photo shows the wired-up socket I used with a PROM reader; the text note describes wiring and use. the adapter is only for reading, not for writing.

The three ROMS were dumped; here's the contents as Intel hex records. ROM 1B; ROM 3B; ROM 5B. the resulting data is likely Z80 code. I recognize C31520 as a "jump 2015" in the 1B ROM and so on.

Again, details of the adapter are on the text document linked above. Here's a wiring diagram of the 24-pin socket between the 82S181, and the ZIP socket of the PROM programmer used to read:

82S181	pin		ET2716
Vcc ------- 24 -------- Vcc
A8  ------- 23 -------- A8
A9  ------- 22 -------- A9
/CE1 ->GND  21          Vpp=5V
/CE2 ------ 20 -------- /OE
CE3 ------- 19 -------- A10
CE4 -->+5V  18          /CE

- Herb Johnson

Similar adapter to read 7641 bipolar PROMS

I was contacted by Joakim Larsson in Dec 2015, who used the PROM adapter info on this Web page to make a similar adapter for PROMs he wanted to read. - Herb

"I used a modified version of your adapter design and could successfully read out two Harris 7641 bipolar 512x8 proms today. You can see some pictures on the Swedish electronics forum [at this Web link]. It will eventually become a contribution to the MESS [computer emulator] project. Thanks!" - Joakim

The link is to the Elektronik - Allmänt forum, subject line "Laga Esselte 100 (skoldator". Google translate or other Web services may provide a translation of that Swedish language Web page. Here's an extracted photo of the socket Joakim wired-up.

here's the wiring he used, to read a 7641 as a ET2716:

7641-5 pin      ET2716
Vcc ------- 24 -------- Vcc
A8 -------- 23 -------- A8
NC -------- 22          A9
/CE1 ->GND  21          Vpp=5v
/CE2 ------ 20 -------- /OE
CE3 ------- 19 -------- A10
STR -->Vcc  18          /CE
GND ------- 12 -------- GND 

- Herb, with quotes from Joakim Larsson

Herb Johnson
New Jersey, USA
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Copyright © 2016 Herb Johnson