11 Mar
2007
11 Mar
'07
1:53 a.m.
I'm thinking of a device that would step down the speed of an rs232
connection from, say, 9600 to 110. The idea is to allow a computer that
can't do 110 to talk to an ASR33 teletype. Does such a device exist?
What's it really called? Does anyone have any schematics for one?
--
David Griffith
dgriffi at cs.csubak.edu
A: Because it fouls the order in which people normally read text.
Q: Why is top-posting such a bad thing?
A: Top-posting.
Q: What is the most annoying thing in e-mail?
11 Mar
11 Mar
4:40 a.m.
I'm thinking of a device that would step down the
speed of an rs232
connection from, say, 9600 to 110. The idea is to allow a computer that
can't do 110 to talk to an ASR33 teletype. Does such a device exist?
What's it really called? Does anyone have any schematics for one?
I have devices that will do this - these are actually RS-232 data switches
that I designed in the 80s. It was a whole line ranging in size from 8 to 56
ports, once a connection is made, the ends operate with independant
interfaces, and the switch mediates between them.
For what you want to do you only need two ports. You will also need either
some kind of flow control (RTS/CTS, XON/XOFF etc.) on the faster speed
port, or a buffer large enough to contain the maximum possible data block
that will be sent to the slower-speed port before the system waits for a
response from it.
Easy to design and build - a single-chip micro with two serial ports would
fit the bill nicely, otherwise you could bit-bash the slow speed port, or
use an external UART. Simply set the speed/parity/Dbits/Sbits that you want
for each port, then copy data between them through buffers - when a buffer
approaches full, assert flow control on the filling port, when the buffer
later approaches empty, deassert flow control on the filling port.
Dave
--
dave06a (at) Dave Dunfield
dunfield (dot) Firmware development services & tools: www.dunfield.com
com Collector of vintage computing equipment:
http://www.classiccmp.org/dunfield/index.html
5:22 a.m.
On Sun, 11 Mar 2007, Dave Dunfield wrote:
I'm not very keen on microcontroller hacking. Which one would you
recommend for something like this? I'm guessing that for a fixed-speed
job, you'd have the microcontroller, two MAX232 chips, and not much else.
--
David Griffith
dgriffi at cs.csubak.edu
A: Because it fouls the order in which people normally read text.
Q: Why is top-posting such a bad thing?
A: Top-posting.
Q: What is the most annoying thing in e-mail?
I'm
thinking of a device that would step down the speed of an rs232
connection from, say, 9600 to 110. The idea is to allow a computer that
can't do 110 to talk to an ASR33 teletype. Does such a device exist?
What's it really called? Does anyone have any schematics for one?
I have devices that will do this - these are actually RS-232 data switches
that I designed in the 80s. It was a whole line ranging in size from 8 to 56
ports, once a connection is made, the ends operate with independant
interfaces, and the switch mediates between them.
For what you want to do you only need two ports. You will also need either
some kind of flow control (RTS/CTS, XON/XOFF etc.) on the faster speed
port, or a buffer large enough to contain the maximum possible data block
that will be sent to the slower-speed port before the system waits for a
response from it.
Easy to design and build - a single-chip micro with two serial ports would
fit the bill nicely, otherwise you could bit-bash the slow speed port, or
use an external UART. Simply set the speed/parity/Dbits/Sbits that you want
for each port, then copy data between them through buffers - when a buffer
approaches full, assert flow control on the filling port, when the buffer
later approaches empty, deassert flow control on the filling port. 
6:44 a.m.
I'm not very keen on microcontroller hacking.
Which one would you
recommend for something like this? I'm guessing that for a fixed-speed
job, you'd have the microcontroller, two MAX232 chips, and not much else.
Try something AVR (an Atmega 32 as an example) and BASCOM from
www.mcselec.com
The code is very simple. Try to hack something and if you don't succeed,
drop me a personal mail, I cannot cope sometimes with the activity of this
list, although I love to read it.
Greetz from Brazil
Alexandre Souza
www.tabajara-labs.com.br
7:08 a.m.
> Easy to design and build - a single-chip micro
with two serial ports
would
> fit the bill nicely, otherwise you could bit-bash
the slow speed port,
or
> use an external UART. Simply set the
speed/parity/Dbits/Sbits that you
want
> for each port, then copy data between them
through buffers - when a
buffer
> approaches full, assert flow control on the
filling port, when the
buffer
later
approaches empty, deassert flow control on the filling port.
I'm not very keen on microcontroller hacking. Which one would you
recommend for something like this? I'm guessing that for a fixed-speed
job, you'd have the microcontroller, two MAX232 chips, and not much else.
8:40 a.m.
I'm not very keen on microcontroller hacking.
Which one would you
recommend for something like this? I'm guessing that for a fixed-speed
job, you'd have the microcontroller, two MAX232 chips, and not much else.
Doesn't much matter - the task is simple enough that pretty much any
architecture will work. Heres some things to consider when selecting
one:
- Two UARTS - as noted previously this is not a show-stopper requirement,
however it will make your life a lot easier. The alternatives are to
bit-bash the slower port which requires careful timing and/or interrupts
and is probably not a good starter project, or to add an external UART -
which means you will have to wire an external bus.
- Internal RAM. The more the better, because the larger you can make your
buffers, the more efficient your flow control will be (there's always
some small delay with starting/stopping ... especially of you need to
use XON/XOFF type control). Assuming you have flow control available,
then 128-256 bytes in each direction should be fine (if the fast computer
never asserts flow control on receive data then you could get away with
less (none) on the slow->fast direction. If the fast side does not accept
fow control, then you are going to need a LOT of buffer in the fast->slow
direction and you will most likly have to wire an external bus with
external memory. With hardware flow control you can probably get away
with less, XON/XOFF you might get away with 64 - I've seen 30-40+ characters
come out of some devices AFTER the XOFF character was received, so plan
your code accordingly.
- Flash based - if don't have programming tools, embedded debuggers etc.
a flash based MCU will be much easier to work with - normally you just
need a cable to your PC and you simply reload code directly into the
microcontroller flash.
- Any of the 8-bit Motorola, Intel, Atmel or many others should do fine,
use the above criteria to pick a really suitable one.
Dave
--
dave06a (at) Dave Dunfield
dunfield (dot) Firmware development services & tools: www.dunfield.com
com Collector of vintage computing equipment:
http://www.classiccmp.org/dunfield/index.html
8:41 a.m.
My recollection is very foggy as I never had a chance to use one of
these things, but there were devices (inexpensive) to do this for use
with printers (at least in one direction) that would not only buffer
up data to be printed, but also do protocol conversions (parallel-to-
serial, serial-to-parallel). If someone had a very old Inmac catalog
from the 80's, I suspect you might find something
there.
There were also devices for sharing terminals on a single port sold
by Inmac and several other companies.
Finding one of these devices themselves would be harder as I suspect
that most have long been discarded as peripheral "junk". In a snap,
almost any old PC with two serial ports could be programmed to do
the same thing.
Cheers,
Chuck
12:44 p.m.
that most have long been discarded as peripheral
"junk". In a snap,
almost any old PC with two serial ports could be programmed to do
the same thing.
Another idea (less bulk) would be to wire a microcontroller ton an ISA
card with 2 serial ports (either a dual async card or a mulit-I/O card,
or whatever). This would save you having to wire up the RS232 buffers, it
would also avoid having to bit-bang either port (I have this ingrained
dislike of bit-banger serial ports....)
-tony
24 Mar
24 Mar
2:43 p.m.
On 3/11/07 10:41 AM, "Chuck Guzis" <cclist at sydex.com> wrote:
My recollection is very foggy as I never had a chance
to use one of
these things, but there were devices (inexpensive) to do this for use
with printers (at least in one direction) that would not only buffer
up data to be printed, but also do protocol conversions (parallel-to-
serial, serial-to-parallel). If someone had a very old Inmac catalog
from the 80's, I suspect you might find something there.
There were also devices for sharing terminals on a single port sold
by Inmac and several other companies.
Finding one of these devices themselves would be harder as I suspect
that most have long been discarded as peripheral "junk". In a snap,
almost any old PC with two serial ports could be programmed to do
the same thing.
Cheers,
Chuck
I picked up a few of these devices, unused in the box, with the Xerox Stars
I found recently. They are called the "PCS/2000 Networking Modem" by
Microcom. They are Z-80 based, have 2 independent RS-232 interfaces
allowing communication at different baud rates from 110 to 9600, and provide
Xon/Xoff flow control. Now I just need to convert the current loop on my
ASR-33 to RS-232 so I can try it out.
Richard Lynch
11 Mar
11 Mar
12:33 p.m.
I have devices that will do this - these are actually RS-232 data switches
that I designed in the 80s. It was a whole line ranging in size from 8 to 56
In fornt of me i have something called a 'NetCommander' made by 'Digitial
Products In (the SUB-LAN Company)'. It's got 16 RS232 ports, and you can
tell it to 'connect' any port to any other port with different baud rates
on the 2 sides. The Rs232 ports are on plug-in cards (2 ports to a card),
so I guess parallel cards also existed. I do have a smaller one, all on
one baord, with 6 RS232 ports and 4 parallel ports IIRC.
Never done much with it, maybe I should...
-tony
12:28 p.m.
I'm thinking of a device that would step down the speed of an rs232
connection from, say, 9600 to 110. The idea is to allow a computer that
can't do 110 to talk to an ASR33 teletype. Does such a device exist?
Are there many computers (apart from the BBC Micro!) that can do 9600
baud but not 110 baud? I ask merely for information.
What's it really called? Does anyone have any
schematics for one?
I believe it's a subset of the functionality of an RS232 'protocol
convereter'. Of course 'protocol conmverter' covers a lot more than
things with an RS232 itnerface on each side, but I've references to units
that will change baud rates, parity, etc.
I have a thing called a 'Ferret'. It comes in an attache' case sort of
housing, and it has the lights-n-switches of an RS232 breakout box, a
couple of ZIF sockets, cassette interface jacks, D-connectors for RS232,
current loop, and parallel, a keypad., LCD display, and strip printer.
Amongst the features of this unit is that it will interface between Rs232
and current loop _with different baud rates on the 2 interfaces_. Sounds
like just what you need, but no idea where you'd find one. BTW, it'll
also do serial (Rs232 or current loop) to parallel interfaceing, work as
an EPROM programmer, print out data from either serial interface, act as
a line monitor on an RS232 interfacem etc. You can even program it
yourself in Z80 machine code.
'Electronics, The Maplin Magazine' (A UK electronics mag, now long
defunct, published by Maplin who were a major hobbyist component supplier
back then [1]) did a series of projects to make a RTTY station. One of
them was a baud/protocol convereter (to converter bwrween 5-bit 45.5 baud
RTTY and, say, an 8 bit 1200 baud computer serial port). IIRC, it was a
couple of dumb40 pin UART, some kind of clock gneerator, and a little
(very little) glue logic. Agai, I have no idea where you'd find the
article now, but it did include a schematic.
[1] Maplin, the company, are still going, but their range of components
is a joke. They now mostly sell electornic toys, Lo-Fi, etc.
-tony
1:29 p.m.
On Sun, 11 Mar 2007, Tony Duell wrote:
The Spare Time Gizmos SBC6120 (single board pdp8e clone) allows 38,400,
9600, 1200, and 300. There's a permanent mod that adds 110, but I'm put
off by the permanent part. You also lose the 38,400 setting.
--
David Griffith
dgriffi at cs.csubak.edu
A: Because it fouls the order in which people normally read text.
Q: Why is top-posting such a bad thing?
A: Top-posting.
Q: What is the most annoying thing in e-mail?
I'm
thinking of a device that would step down the speed of an rs232
connection from, say, 9600 to 110. The idea is to allow a computer that
can't do 110 to talk to an ASR33 teletype. Does such a device exist?
Are there many computers (apart from the BBC Micro!) that can do 9600
baud but not 110 baud? I ask merely for information.
1:54 p.m.
Are there many
computers (apart from the BBC Micro!) that can do 9600
baud but not 110 baud? I ask merely for information.
The Spare Time Gizmos SBC6120 (single board pdp8e clone) allows 38,400,
9600, 1200, and 300. There's a permanent mod that adds 110, but I'm put
off by the permanent part. You also lose the 38,400 setting.
2:29 p.m.
On Sun, 11 Mar 2007, Tony Duell wrote:
Does it support hardware flow control on the console port? If not, then
you're going to have a problem if the machine is seding characters at,
say, 1200 (about 120 cps) baud and your tty is only taking them at 110
baud (about 10 cps, since 110 baud often implies 2 stop bits). You've
got to have a way to tell the faster side to stop sending for a bit.
I'm not sure. I just want to drop 300 down to 110.
Are there many computers (apart from the BBC Micro!)
that can do 9600
baud but not 110 baud? I ask merely for information.
The Spare Time Gizmos SBC6120 (single board pdp8e clone) allows 38,400,
9600, 1200, and 300. There's a permanent mod that adds 110, but I'm put
off by the permanent part. You also lose the 38,400 setting. What does the mod consist of? I can't believe
it's really permanent
(although it might well involve soldering to undo it). Losing 38400 buad
is surely not a problem, since few, if any, classic terminals ran at that
speed, and you don't _need_ that sort of data rate for a tectual terminal
anyway.
The mod is discussed in this post:
http://groups.yahoo.com/group/sparetimegizmos/message/580
--
David Griffith
dgriffi at cs.csubak.edu
A: Because it fouls the order in which people normally read text.
Q: Why is top-posting such a bad thing?
A: Top-posting.
Q: What is the most annoying thing in e-mail?
6:04 p.m.
I'm not sure. I just want to drop 300 down to
110.
Even so, that's 30 cps from the machine (300 baud at 10 bits/char,
including start and 1 stop bit) and 10 cps to the teletype (110 baud at
11 bis/chat including start and 2 stop bits). You've still got to have
some wat to slow the machine down or stop it sending.
-tony
5:48 p.m.
From: "Tony Duell" <ard at p850ug1.demon.co.uk>
It doesn't, as-shipped, though I see enough spares in the the schematic
to implement RTS flow control.
The Spare Time
Gizmos SBC6120 (single board pdp8e clone) allows 38,400,
9600, 1200, and 300. There's a permanent mod that adds 110, but I'm put
off by the permanent part. You also lose the 38,400 setting.
Does it support hardware flow control on the console port? If not, then
you're going to have a problem if the machine is seding characters at,
say, 1200 (about 120 cps) baud and your tty is only taking them at 110
baud (about 10 cps, since 110 baud often implies 2 stop bits). You've
got to have a way to tell the faster side to stop sending for a bit. What does the mod consist of? I can't believe
it's really permanent
(although it might well involve soldering to undo it). Losing 38400 buad
is surely not a problem, since few, if any, classic terminals ran at that
speed, and you don't _need_ that sort of data rate for a tectual terminal
anyway.
The baud rate generator is a 4.9152Mhz can oscillator, a 74HC4040
divider, a header and some jumpers. So, the hack is to simply
replace the oscillator with a 1.804Mhz one. I've never seen a
can of that frequency, though, and substituting a 1.8432Mhz
oscillator would leave you about 2% too fast. 3.579Mhz comes
within a percentage point, but you'd need to tap a different
pin on the divider, which would probably involve a blue wire.
(I used sockets for the oscillator cans on mine, so changing
can would be easy for me.)
Vince
6:14 p.m.
> Does it support hardware flow control on the
console port? If not, then
[...]
It doesn't, as-shipped, though I see enough spares
in the the schematic
to implement RTS flow control.
Which owuld presumably be another 'blue wire' mod.
What does the mod consist of? I can't believe
it's really permanent
(although it might well involve soldering to undo it). Losing 38400 buad
is surely not a problem, since few, if any, classic terminals ran at that
speed, and you don't _need_ that sort of data rate for a tectual terminal
anyway.
The baud rate generator is a 4.9152Mhz can oscillator, a 74HC4040
divider, a header and some jumpers. So, the hack is to simply replace the oscillator with a 1.804Mhz one. I've
never seen a
can of that frequency, though, and substituting a 1.8432Mhz
oscillator would leave you about 2% too fast. 3.579Mhz comes
Which would be near enough. I once used a 555 timer as a baud rate
generator, and had no problems at all. Used 1% R's and C's, nearest
standard values to the ones I'd calculated (I forget what they were), and
had no tweeaks. Never had any problems with it.
If the use of the links is the obvious one (that is, to select outputs of
the '4040 and feed it into some more circuitry), you could make an
external PCB with an osiccilator and divider chip on it and connect the
output to the appropriate pin on the jumper block.
-tony
7:46 p.m.
From: "Tony Duell" <ard at p850ug1.demon.co.uk>
Yes, though thinking about it some more, I realized it wasn't RTS
flow control that is needed (like "reader-run"), but CTS flow control.
I don't see a simple way to implement that with what's there.
[I'm thinking that ANDing "transmit empty" from the UART and CTS
(buffered through the spare receiver in the MAX232) should work
to clock the HC74 being used to implement the "done" flop. I don't
see the gate, though -- there's a half an HC74 free, but that's
about it.]
> Does it
support hardware flow control on the console port? If not, then
[...]
It doesn't, as-shipped, though I see enough
spares in the the schematic
to implement RTS flow control.
Which owuld presumably be another 'blue wire' mod. If the use of the links is the obvious one (that is,
to select outputs of
the '4040 and feed it into some more circuitry), you could make an
external PCB with an osiccilator and divider chip on it and connect the
output to the appropriate pin on the jumper block.
Yes, that would work. One whole side of the 4x2 header used to jumper
baud rates is directly connected to the UART, so it just needs a CMOS
clock of the right frequency applied there, and the shorting block
removed altogether.
Vince
12 Mar
12 Mar
3:39 p.m.
If the use of
the links is the obvious one (that is, to select outputs of
the '4040 and feed it into some more circuitry), you could make an
external PCB with an osiccilator and divider chip on it and connect the
output to the appropriate pin on the jumper block.
Yes, that would work. One whole side of the 4x2 header used to jumper
baud rates is directly connected to the UART, so it just needs a CMOS
clock of the right frequency applied there, and the shorting block
removed altogether.
4:44 p.m.
From: "Tony Duell" <ard at p850ug1.demon.co.uk>
Correct.
Vince
Yes, that
would work. One whole side of the 4x2 header used to jumper
baud rates is directly connected to the UART, so it just needs a CMOS
clock of the right frequency applied there, and the shorting block
removed altogether.
I'm assuming the other row of that 4*2 block goes to outputs on the
HC4040. 
5:42 p.m.
New subject: Netframe collectors?
Does anyone here collect Netframes?
Not the later Micron crap, I'm talking about the early Netframes like
the little mushroom unit and the 3' monolith units that ran Novell and
you connected to admin it via a Novell SPX client.
Also looking for anyone who collects Tricord ES7000 and ES8000 servers.
Curt
14 Mar
14 Mar
11:28 p.m.
New subject: Netframe collectors?
I have always been interested in getting an earlier NetFrame to play around
with. Do you have something in particular you are looking to unload?
Depending on where you are I could be very interested.
Greg Manuel
-----Original Message-----
From: Curt - Atari Museum [mailto:curt at atarimuseum.com]
Sent: Monday, March 12, 2007 8:43 PM
To: General Discussion: On-Topic and Off-Topic Posts
Subject: Netframe collectors?
Does anyone here collect Netframes?
Not the later Micron crap, I'm talking about the early Netframes like
the little mushroom unit and the 3' monolith units that ran Novell and
you connected to admin it via a Novell SPX client.
Also looking for anyone who collects Tricord ES7000 and ES8000 servers.
Curt
15 Mar
15 Mar
6:45 a.m.
New subject: Netframe collectors?
Hi,
I am looking for an NF250 and NF450 myself :-)
Curt
G Manuel (GMC) wrote:
I have always been interested in getting an earlier
NetFrame to play around
with. Do you have something in particular you are looking to unload?
Depending on where you are I could be very interested.
Greg Manuel
-----Original Message-----
From: Curt - Atari Museum [mailto:curt at atarimuseum.com]
Sent: Monday, March 12, 2007 8:43 PM
To: General Discussion: On-Topic and Off-Topic Posts
Subject: Netframe collectors?
Does anyone here collect Netframes?
Not the later Micron crap, I'm talking about the early Netframes like
the little mushroom unit and the 3' monolith units that ran Novell and
you connected to admin it via a Novell SPX client.
Also looking for anyone who collects Tricord ES7000 and ES8000 servers.
Curt
8:33 a.m.
New subject: Netframe collectors?
On Thursday 15 March 2007 06:45, Curt - Atari Museum wrote:
Hi,
I am looking for an NF250 and NF450 myself :-)
Over the past year, I've seen a few Netframes "pass-through" scrappers. If
folks are interested in Netframes, I will ask them to watch for them.
I have no idea of what a Netframe should go for pricewise. Email me privately
with what you think would be a fair price. I won't pass your individual
numbers to the scrappers - but will create an "average" number as an
"incentive" for them to "watch" and call me. If I hear of one being
available, I'll post that info to the list.
As you can see from my signature, I'm located in Silicon Valley, so consider
shipping charges if you aren't local.
Cheers,
Lyle
--
Lyle Bickley
Bickley Consulting West Inc.
Mountain View, CA
http://bickleywest.com
"Black holes are where God is dividing by zero"
11 Mar
11 Mar
2:56 p.m.
Are there many computers (apart from the BBC Micro!)
that can do 9600
baud but not 110 baud? I ask merely for information.
I've see a number - for various reasons.
- Some use DIP switches to set the rate, so the limit it to "common"
settings, and in post-TTY days, "nobody uses 110".
- Some use an off-the shelf baud rate generator (often tied into a
UART like the 6552), and for whatever reasons, provided it with 1/2
the rate clock - this 300 becomes 150, 600 becomes 300, 1200 becomes
600 etc.... since the off-the-shelf parts don't do 220, 110 gets
lost.
- Some just don't "feel" like offering all the available options
provided by the hardware.
Another idea (less bulk) would be to wire a
microcontroller ton an ISA
card with 2 serial ports (either a dual async card or a mulit-I/O card,
or whatever). This would save you having to wire up the RS232 buffers, it
would also avoid having to bit-bang either port (I have this ingrained
dislike of bit-banger serial ports....)
If the device is dedicated to <high-speed> to 110 bps conversion, bit-bang
might make sense - At 110, bit-bang is pretty easy, and can be accomplished
with a simple interrupt without too much overhead (and what overhead it does
cause isn't enough to swamp the box which is doing a very simple function
otherwise). I'd go bit-bang for the 110bps port on a single-chip micro before
I'd go to the hassle of wiring up an external bus, no matter it it's to an
ISA card or another dedicated UART.
As someone else pointed out, if size & power requirements are not a concern,
this would be very easily done with an old PC - even an XT would have plenty
of go for this job.
Dave
--
dave06a (at) Dave Dunfield
dunfield (dot) Firmware development services & tools: www.dunfield.com
com Collector of vintage computing equipment:
http://www.classiccmp.org/dunfield/index.html
3:08 p.m.
On 11/03/07, Tony Duell <ard at p850ug1.demon.co.uk> wrote:
Are there many computers (apart from the BBC Micro!)
that can do 9600
baud but not 110 baud? I ask merely for information.
I am fairly sure I persuaded a beeb to do 110 once, for dial-up to a
cetain university to play MUD.. I think it was as simple as changing a
jumper over, but this was about 25 years ago and so i forget exactly
which one.. It was certainly a non-permenant mod..
On 11/03/07, Tony Duell <ard at p850ug1.demon.co.uk> wrote:
[1] Maplin, the company, are still going, but their range of components
is a joke. They now mostly sell electornic toys, Lo-Fi, etc.
Tell me about it... I cleaned out two stores this weekend to get
enough 33uF 25V electrolytics for a repair I was doing... hardly
exotic, I thought, but the total quantity between two stores? Five!
Rob
3:59 p.m.
On Sun, 11 Mar 2007, Rob wrote:
On 11/03/07, Tony Duell <ard at
p850ug1.demon.co.uk> wrote:
Sounds like Radio Shack here in the US.
--
David Griffith
dgriffi at cs.csubak.edu
A: Because it fouls the order in which people normally read text.
Q: Why is top-posting such a bad thing?
A: Top-posting.
Q: What is the most annoying thing in e-mail?
[1] Maplin, the company, are still going, but their range of components
is a joke. They now mostly sell electornic toys, Lo-Fi, etc.
Tell me about it... I cleaned out two stores this weekend to get
enough 33uF 25V electrolytics for a repair I was doing... hardly
exotic, I thought, but the total quantity between two stores? Five!
6:19 p.m.
Are there many
computers (apart from the BBC Micro!) that can do 9600
baud but not 110 baud? I ask merely for information.
I am fairly sure I persuaded a beeb to do 110 once, for dial-up to a
cetain university to play MUD.. I think it was as simple as changing a
jumper over, but this was about 25 years ago and so i forget exactly
which one.. It was certainly a non-permenant mod..
On 11/03/07, Tony Duell <ard at p850ug1.demon.co.uk> wrote:
I've beem told that 1k resistors (that's the standard, 0.6W 1% resistors,
nothing exotic) are 'order only' components at some shops.
-tony
[1] Maplin, the company, are still going, but their range of components
is a joke. They now mostly sell electornic toys, Lo-Fi, etc.
Tell me about it... I cleaned out two stores this weekend to get
enough 33uF 25V electrolytics for a repair I was doing... hardly
exotic, I thought, but the total quantity between two stores? Five!
12 Mar
12 Mar
12:42 a.m.
On 12/03/07, Tony Duell <ard at p850ug1.demon.co.uk> wrote:
Having had a quick squint (well it is 7am) at the beeb schematics, I'm
pretty sure it was changing S28/S29 - these alter the inputs to IC42,
a 74LS164 4 bit counter, used as a divider on the clock input to the
Serial ULA The only referance to these I can find online now is that
you can alter the cassette from 1200 to 1300 baud using them, so that
sounds like it's the right place. It was definitely a "change the
jumper(s) and set to x baud rate and it'll actually do y". It may
not have been the exact rate, but it was close enough that it was used
on a dial up to a 110baud port with no problem. (The dial-up used
totally dumb modem normally used for 300bps...)
Rob
I am fairly sure I persuaded a beeb to do 110 once, for dial-up to a
cetain university to play MUD.. I think it was as simple as changing a
jumper over, but this was about 25 years ago and so i forget exactly
which one.. It was certainly a non-permenant mod..
I wasn't aware of any such jumper... The baud rate generator in the Beeb
is inside the Serial ULA (the acutal serial chip is a 6850), and I didn't
think there was any way to get that to generate the appropratie output
frequency.
1:43 a.m.
On 12/03/2007 07:42, Rob wrote:
On 12/03/07, Tony Duell <ard at
p850ug1.demon.co.uk> wrote:
Having had a quick squint (well it is 7am) at the beeb schematics, I'm
pretty sure it was changing S28/S29 - these alter the inputs to IC42,
a 74LS164 4 bit counter, used as a divider on the clock input to the
Serial ULA
That's right, and it's a standard mod, described in Acorn's notes.
Changing S28 increases the baud rate so you get 108 baud instead of 75.
It affects the cassette baud rate as well, of course.
--
Pete Peter Turnbull
Network Manager
University of York
I am
fairly sure I persuaded a beeb to do 110 once, for dial-up to a
cetain university to play MUD.. I think it was as simple as changing a
jumper over, but this was about 25 years ago and so i forget exactly
which one.. It was certainly a non-permenant mod..
I wasn't aware of any such jumper... The baud rate generator in the Beeb
is inside the Serial ULA (the acutal serial chip is a 6850), and I didn't
think there was any way to get that to generate the appropratie output
frequency. 
8:03 a.m.
Rob wrote:
but but but... go to their website. Their logo states "Maplin, the electronics
specialist" :-)
I totally agree with you - if the stores exist to sell the same gimmicky junk
that can be had cheaper elsewhere, then I'm not sure why they have the stores
at all and can't put the huge rental / staffing costs to better use.
H. Gee's in Cambridge is a real blessing in comparison - wide range of
components and still staffed by people who know what they're talking about
(and are helpful enough to direct you elsewhere if they know of somewhere
locally that's cheaper or has exactly what you need - always the sign of a
good shop!)
Hmm, which makes me wonder if we shouldn't have a section on the classiccmp
website for recommended places to get spares/components from?
cheers
Jules
[1] Maplin,
the company, are still going, but their range of components
is a joke. They now mostly sell electornic toys, Lo-Fi, etc.
Tell me about it... I cleaned out two stores this weekend to get
enough 33uF 25V electrolytics for a repair I was doing... hardly
exotic, I thought, but the total quantity between two stores? Five! 
10:46 a.m.
Jules Richardson wrote:
Rob wrote:
>> [1] Maplin, the company, are still going, but their range of components
>> is a joke. They now mostly sell electornic toys, Lo-Fi, etc.
So who sells Hi-Fi that you can afford?
Well the UK still for the moment makes the best speakers - Lowthers.
> Tell me about it... I cleaned out two stores this
weekend to get
> enough 33uF 25V electrolytics for a repair I was doing... hardly
> exotic, I thought, but the total quantity between two stores? Five!
The key word here is *Repair*.
but but but... go to their website. Their logo states
"Maplin, the
electronics specialist" :-)
We have the same kind of stores here, other than a few things
like fuses I have have to mail order for components.
Hmm, which makes me wonder if we shouldn't have a
section on the
classiccmp website for recommended places to get spares/components from?
Also how many items are in stock would be useful too for spares.
cheers
Jules
2:08 p.m.
On 12/03/07, woodelf <bfranchuk at jetnet.ab.ca> wrote:
That I don't know 'owt about...
I think it says somthing of their current target audience type that
their newest stores are all in big edge-of-town retail parks..
Quite.. this was a rescued linksys wireless router.. they are prone to
failing with to bad caps in the switch circuits. So 55p ($1) of
components later and it's working again.. (mostly.. the adsl side is
still playing up.) I'm not up to Tony's level of getting dirty with
circuitry, but when it's that simple a fix, I'll do it. I think
though even I am in a minority here.. most people would just chuck it
and buy a new one..
Rob
Jules Richardson wrote:
> Rob wrote:
actually I think it might have been Tony who said:
>> [1] Maplin, the company, are still going, but their range of components
>> is a joke. They now mostly sell electornic toys, Lo-Fi, etc.
So who sells Hi-Fi that you can afford?
Well the UK still for the moment makes the best speakers - Lowthers.
> Tell me
about it... I cleaned out two stores this weekend to get
> enough 33uF 25V electrolytics for a repair I was doing... hardly
> exotic, I thought, but the total quantity between two stores? Five!
The key word here is *Repair*.
4:09 p.m.
> Tell me about it... I cleaned out two stores
this weekend to get
> enough 33uF 25V electrolytics for a repair I was doing... hardly
> exotic, I thought, but the total quantity between two stores? Five!
The key word here is *Repair*. Hmm, which
makes me wonder if we shouldn't have a section on the
classiccmp website for recommended places to get spares/components from?
Also how many items are in stock would be useful too for spares.
11 Mar
11 Mar
6:17 p.m.
On 11/03/2007 09:53, David Griffith wrote:
I'm thinking of a device that would step down the
speed of an rs232
connection from, say, 9600 to 110. The idea is to allow a computer that
can't do 110 to talk to an ASR33 teletype. Does such a device exist?
What's it really called? Does anyone have any schematics for one?
I have a device called a MicroFazer that will do this. It was actually
sold as a printer buffer, but it has serial as well as parallel input,
and serial and parallel output, with several hundred K of buffer in
between.
--
Pete Peter Turnbull
Network Manager
University of York
6483
days inactive
6496
days old
36 comments
15 participants
participants (15)
-
alexandre-listas＠e-secure.com.br -
ard＠p850ug1.demon.co.uk -
bfranchuk＠jetnet.ab.ca -
cclist＠sydex.com -
curt＠atarimuseum.com -
dave06a＠dunfield.com -
dgriffi＠cs.csubak.edu -
gmanuel＠gmconsulting.net -
julesrichardsonuk＠yahoo.co.uk -
lbickley＠bickleywest.com -
pete＠dunnington.plus.com -
richardlynch3＠tx.rr.com -
robert＠irrelevant.com -
steerex＠mindspring.com -
vrs＠msn.com