tqk70.txt
Hi PDP-11 people!

I wrote recently about TK70 <-> TQK70 interface
but noone seems to answer. Now I've found some
enginering sketches and notes made by soviet engineers
reverse-engineering some digital tape drive.
(Don't ask me how I'd get them

There are no info regarding type of that drive but
it has Q-BUS controller, and is a cartridge tape drive
with moveable head. Below are the signal names and functions
used between a drive and controller (unfortunately without pin numbers).
For me it seems very close to TK70
functionality. Here they are:

1. From controller to drive:

DS - drive select
RST - reset
TK0 -|
TK1 |- track select
TK2 |
TK3 -|
CO - cassete operate. (Tape moves)
REV - reverse tape movement
HSP - high speed
EEN - erase enable
WEN - wtrite enable
WDA- | write data in differential format
WDA+ |
THR - read comparator threshold
HC - high coercitivity media

2. From drive to controller:
SLD - drive selected
CIN - cassete inserted
USF - erasure and recording enabled
ROP - read data
UTH - upper tape mark
LTH - lower tape mark
TCH - tacho pulses

There are also some details regarding fucntions of abovementioned signals:
UTH and LTH are binary coded:
11 - beginning of tape
01 - load point
10 - early warning
00 - end of tape.

Recording density is 384 bits/millimeter
HSP signal is used when high drfive speed is used for fast winding only.
Tape transfer speed is about 2.29 meters/sec.
EEN signal enables bulk erasure for whole tape width.
TK0-TK3 signals are coded as follows:
0000...1000 - tracks 0..8
110X and 111X - offset head upper or lower respectively relative to selected
track. X value is 0 for tracks 0, 2, 4 ,6, 8 and 1 for tracks 1, 3, 5, 7
Signals must present at least 500 uSEC.

Now this interface seems very suitable for TK50/TK70 functionality but also
it might be QIC dirve. But QIC dirves don't have "Load point" at the tape!

The question to anyone who participated in TK70/TQK70 development -
is this the interface they use?

Sincerelly,
Stacy.
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