In article . com,
wrote:
I have schematics..

there is PCB 483 (CPU with tape recorder port)
there is PCB 493 (CPU with tape port, also 1 rs232 port)

O.K.

I have 483, tape port only...

Interesting -- because the web page to which I pointed said that
the tape drive was serial and the same port could be used for other
RS-232 devices.

it is 8085 processor. tape port data lines come directly off
a 8155 chip

O.K. And an 8155 is a PIO (parallel I/O) chip similar to the
Motorola 6820 (except designed to interface to a different system bus).

Note that a Parallel I/O port can be used to talk to serial
(RS-232) devices (called a "bit-banger" interface). The original SWTP
6800 computer used a few pins on a 6820 to talk to the terminal which
served as a console, instead of using the 6850 chip (ACIA -- serial port
chip). This was done because the serial chip was not yet in production
when Motorola designed the first breadboard computer and ROM for
engineers to play with.

In this case, the reason for doing a bit-banger on a parallel
I/O chip is because of all of the sense and control leads which the tape
drive needs. It could *still* be wired as an RS-232 interface, as long
as you ignore enough of the spare pins. This is why I've been asking
what connections go to which pins on the connector.

"The 8155/8156 is a very old combination chip containing 256*8 RAM,
a timer and 8+8+6 ports."

Yes, I agree.

the 8155 has d0-d7 from the 8085 CPU connected, as well as reset,
RD/WR and a few other CPU pins... The clk (out) from the 8085
is connected to some sort of ?divider?, then routed to the
8155.

Probably generating the bit rate clock which was then fed into
an interrupt pin on the 8155, so it didn't have to do the timing in
software. Hmm ... I don't see an interrupt pin on the 8155, but I do
see a "Timer In" (pin 3 on the chip), which could dserve the function.
The timer is a programmable divider, which could be programmed to
generate the various baud rates needed. Does that divider go to pin 3?
(There are advantages to having antique data books around. :-)

off the 8155 there a

(-xx-) = active low

O 1) DATA OUT data from crusader to tape drive

O.K. Can you trace this and tell me which pin it goes to on the
DB-25 connector? Perhaps one of 2 or 3?

I 2) STOP/(-RUN)- this controls tape drive motor (on/off)
I 3) rewind/(-fwd) this controls direction of tape drive motor
I 4) read/(-write) controls head.. to read or write
I 5) slow/(-fast) controls tape speed. fast = rewind/ffd slow
= read or write
O 6) read data in data from tape drive to crusader

And does this one go to one of pins 2 or 3 on the DB-25
connector?

? 7) a/b don't know

This probably goes to a sensor in the drive which can tell which
side of the tape is out -- for a file big enough to take two tape sides
to save, perhaps.

? 8) leader don't know

Some (though not all) of the tapes of this size have a
transparent leader which could be sensed by a LED and photosensor in the
drive, so the system doesn't start writing until you are past the leader
and onto the writable tape.

O 9) wr protect this is a switch in the recorder. pushes
agains the "write protect" area on the cassette

Sure.

O 10) cassete in place this is a switch in the recorder. pushes
against the cassette

Yep -- to keep from attempting to save to a tape which was not
in the drive.

O 11) play switch \
O 12) record switch to switches on cassete unit
O 13) stop switch /

O = output (output from tape to crusader II computer)
I = input (input from crusader II computer to tape drive)

O.K. Commonly shown as "-" (tape to computer), and "-"
computer to tape.

total of 7 output lines
4 input lines
2 unknowns

I think that I have filled those in for you.

Those aren't pin numbers... just a list.

The pin numbers are important.

I don't think it is rs232 compatible. The data
is sent serially (1 data line), but there are no
timing lines (handshake, etc).

RS-232 does not *use* timing lines. It starts with a "start
bit", then a series of known length of data bits, followed by an
optional parity bit, and one or two stop bits. (Two stop bits were
needed on the ASR-33 teletype, to allow the mechanism time to reset.)

the PCB 493 (which I don't have) has rs232
port built in.

Perhaps a secondary RS-232, instead of a bit-banger interface.

PCB 483 schematic shows a small area
of the circuit that has been "deleted"
by the engineers, it is labeled "deleted-PC499 is
used for serial i/o transmission"

An optional bit of circuitry.

I can't find PCB493 for sale anywhere.. I am
tempted to run a parallel port monitor on
my windows PC, connect the lines from the
tape port to it, and watch what signals do
what when data is saved to the "tape".

If you can verify that the data to and from the cassette are on
pins 2 and 3, I would suggest trying to analyze it as RS-232. When
talking to a computer via RS-232, it would not need to use all of the
pins which talk to the tape drive, and those AUX codes could be to tell
the Crusader to ignore those extra pins while talking to a computer or
something else via RS-232.

I could see what timing/format the data IN
and data OUT pins are using. Perhaps
a communications program on the PC
will be able to talk to the crusader this
way..

I'm still willing to bet (at least until you feed me connector
pin numbers which say that it can't be) that it can and will talk
RS-232. But first use a scope to check the voltages on those pins -- as
the computer might not like the RS-232 + and - voltages into parallel
port (0-5V only) pins.

Or, I could write a C program to "emulate"
the tape drive. example, LOADing a program
into the crusader:

Yes.

You press "get ready for program" on the
crusader.

You would usually then press play on the
recorder. The crusader can detect this
button through the taperecorder cable.

On the PC, you would have a "play" button
on a window, that would make the appropriate
pin on the parallel port go HIGH.

I still believe that you can just use a plain communications
program to talk to it via RS-232. Remember to make the cable as shown
on that web page.

Good Luck,
DoN.
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