On Dec 17, 20:11, John Lawson wrote:
> Sheeesh!!! No excuse for posting before checking references....
>
> Another Senior Moment
We're all having them tonight, it seems :-)
--
Pete Peter Turnbull
Network Manager
University of York
On Dec 18, 0:37, pete@mindy wrote:
> "101100" at 1200, you'll see it's actually a Manchester code:
>
> __ _____ __ __ _____
> | |__| |__| |__| |_____| |
>
> --1-- --0-- --1-- --1-- --0-- --0--
Oops, I take that back :-) Although the Sorcerer manuals describe it as a
Manchester encoder/decoder, what it puts on the tape is FSK. I just
checked the schematic and circuit description.
Dwight hasn't exactly described Manchester encoding either, though.
Manchester encoding puts the clock transition in the *centre* of each
cell, and the polarity of the transition determines whether it's a 0 or a
1. There's a phase shift at the cell boundary if necessary. His diagram
*could* be Manchester encoding if you shift the 0s and 1s slightly to the
left, except for the last bit. It should be (maybe 'd' for "down" and 'u'
for "up" makes it more obvious):
___ _ ___ _ ___
|___| |_| |_| |___|
-0- -1- -1- -0- -0- -1-
d u u d d u
It's too late at night here, for any more of this :-)
--
Pete Peter Turnbull
Network Manager
University of York
I am amazed that Tony didn't mention this, but the BBC micro had a number
of expansion connectors under the keyboard facing towards the front of
the machine. To access these ports, you had to lift the whole machine
and plug IDC terminated ribbon cables. As I recall, you had the 1MHz
expansion bus, the printer port, the Tube (2nd processor bus) and a
disk interface connector. You also had a power output connector allowing
you to power external devices (e.g. external floppies).
The HP Integral PC also had two connectors on the front. These were HIL
connectors for low-speed input devices (keyboard, mouse, digitizing
tablet, etc).
**vp
>From: "Dwight K. Elvey" <dwightk.elvey(a)amd.com>
>
>>From: tlindner(a)ix.netcom.com
>>
>>> Here's one:
>>>
>>> http://www.kim-1.com/usrman.htm#E
>>
>>Ahh, this is really diffferent!
>>
>>This uses:
>>
>>'0 bit' - 18 square cycles at 3700 Hz.
>> 6 square cycles at 2400 Hz.
>>
>>'1 bit" - 9 square cycles at 3700 Hz.
>> 12 square cycles at 2400 Hz.
>>
>>Both are the same length (7.452 microseconds).
>>
>>As you can probably tell, I am currently anaylizing this at a very low
>>level.
>>
>>--
>>tim lindner tlindner(a)ix.netcom.com
>>
>
>Hi
> Here is one that is even a little different still.
>It is what is called Manchester encoding, using biphase
>clocking. You don't indicate 1 or 0, you indicate a change
>by a quick clock and no change by a long clock.
> It looks something like this:
>
> ___ _ ___ _
> |___| |_| |_| |______
Opps! Shuld have been:
___ _ ___ _ ___
|___| |_| |_| |___|
>
> Depending on past history, this might be:
>
> 0 0 1 1 0 0 0
>
> or
>
> 1 1 0 0 1 1 1
>
>
> This is the type of encoding used on my Poly88 for
>what they call PolyPhase. This runs at 2400 baud.
> There is a standard called Byte format that uses 300 baud
>and the two tones 1200 and 2400.
> Besides the type of encoding, you also need to know
>what the record formats looks like. Do you have one long
>record for the entire file? What does the header look like?
>Is it synchronous or asynchronous? Is there parity, check sum,
>CRC or ECC?
> There are a lot of things that need to be built up into
>a complete tape decoder. A tape writer would be used
>by more than a tape reader. One should only need to read
>the tape once but many people would often like to create
>a tape from that same data. You really want both.
> One should also note that most audio tape to digital
>inputs on these old computers filtered the signal some
>to optimize the audio signal for decode. This was done
>on both read and write of the signal.
>Dwight
>
>
>
>From: tlindner(a)ix.netcom.com
>
>> Here's one:
>>
>> http://www.kim-1.com/usrman.htm#E
>
>Ahh, this is really diffferent!
>
>This uses:
>
>'0 bit' - 18 square cycles at 3700 Hz.
> 6 square cycles at 2400 Hz.
>
>'1 bit" - 9 square cycles at 3700 Hz.
> 12 square cycles at 2400 Hz.
>
>Both are the same length (7.452 microseconds).
>
>As you can probably tell, I am currently anaylizing this at a very low
>level.
>
>--
>tim lindner tlindner(a)ix.netcom.com
>
Hi
Here is one that is even a little different still.
It is what is called Manchester encoding, using biphase
clocking. You don't indicate 1 or 0, you indicate a change
by a quick clock and no change by a long clock.
It looks something like this:
___ _ ___ _
|___| |_| |_| |______
Depending on past history, this might be:
0 0 1 1 0 0 0
or
1 1 0 0 1 1 1
This is the type of encoding used on my Poly88 for
what they call PolyPhase. This runs at 2400 baud.
There is a standard called Byte format that uses 300 baud
and the two tones 1200 and 2400.
Besides the type of encoding, you also need to know
what the record formats looks like. Do you have one long
record for the entire file? What does the header look like?
Is it synchronous or asynchronous? Is there parity, check sum,
CRC or ECC?
There are a lot of things that need to be built up into
a complete tape decoder. A tape writer would be used
by more than a tape reader. One should only need to read
the tape once but many people would often like to create
a tape from that same data. You really want both.
One should also note that most audio tape to digital
inputs on these old computers filtered the signal some
to optimize the audio signal for decode. This was done
on both read and write of the signal.
Dwight
On Dec 17, 5:22, vassilip(a)dsl.cis.upenn.edu wrote:
> I am amazed that Tony didn't mention this, but the BBC micro had a number
> of expansion connectors under the keyboard facing towards the front of
> the machine. To access these ports, you had to lift the whole machine
> and plug IDC terminated ribbon cables. As I recall, you had the 1MHz
> expansion bus, the printer port, the Tube (2nd processor bus) and a
> disk interface connector. You also had a power output connector allowing
> you to power external devices (e.g. external floppies).
>From left to right, 34-pin floppy interface, 26-pin parallel printer,
20-pin user port, 34-pin 1MHz bus, 40-pin Tube (second processor
interface).
--
Pete Peter Turnbull
Network Manager
University of York
On Dec 17, 13:50, tim lindner wrote:
> I am looking for information regarding how various computers wrote
> information to audio tapes.
> I am contemplating creating an audio tape anaylzer to help me recover
> some data. I would like to make the program useful to thoes outside the
> Color Computer community. But first I need to understand all of the
> different methods used to put data on audio tape.
Look up "Kansas City" and "CUTS" on the web... many machines used some
derivative.
For 300 baud:
logic 0 is 4 cycles of a 1.2kHz tone
logic 1 is 8 cycles of a 2.4kHz tone
lead-in is 2.4kHz, followed by a zero byte
Similarly for 1200 baud but fewer cycles.
CUTS (Computer Users Tape Interface) was derived from KC format, which was
so called because it came out of a meeting held in Kansas City in 1975.
It's backwards compatible.
Also look up Don Tarbell's system. I can't remember what the tones were,
but it's about 600 baud, IIRC.
None of this tells you about the format of the data, of course -- block
headers (if any), checksums/CRCs, etc. That tended to vary.
--
Pete Peter Turnbull
Network Manager
University of York
Here's one:
http://www.kim-1.com/usrman.htm#E
>From: tlindner(a)ix.netcom.com (tim lindner)
>Reply-To: cctalk(a)classiccmp.org
>To: classiccmp(a)classiccmp.org (Classic Computers)
>Subject: Computer Audio Tape Formats
>Date: Tue, 17 Dec 2002 13:50:31 -0800
>
>I am looking for information regarding how various computers wrote
>information to audio tapes.
_________________________________________________________________
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I am looking for information regarding how various computers wrote
information to audio tapes.
For example, the Tandy Color Computer wrote ones and zeros to audio tape
in the following format:
'one bit': one sinusoidal cycle @ 2400 Hertz.
'zero bit': one sinusoidal cycle @ 1200 Hertz.
The bit rate is variable on a CoCo tape. But averages to about 1500 bits
per second.
I am contemplating creating an audio tape anaylzer to help me recover
some data. I would like to make the program useful to thoes outside the
Color Computer community. But first I need to understand all of the
different methods used to put data on audio tape.
--
tim lindner tlindner(a)ix.netcom.com
Thanks to a post here by Curt Nelson, I am the proud owner now of some
interesting Amiga goodies . . . .
I have a question to all those Amigaphiles out there: I have a copy of
X Window System by GfxBase. It looks like a graphic terminal emulation
for *nix systems, which looks like a neat toy for playing with my Linux
box. Have any of you ever played with this, or even seen it in action?
I do have a 10 Base 2 Ethernet card for the PC here, but other than
that, my networking experience is zero. Looks like I'm going to be
learning some new stuff over the next few months.
Gary Hildebrand
St. Joseph, MO
