Baud rate generator
Paul Johnson
Tx and Rx clock inputs. Can anyone help with information on where to buy
a common part or what to use? I would prefer something thats programable
so I can change the rate on the fly. I've looked at sites like Jameco
and Digikey and gone through their catalogs, and tried to find
information on other sites. The HD-4702 looked like it would be perfect,
but it looks like a military part and I can't find it anywhere. Is there
an equivilent part or very similiar part the major vendors carry that I
can order?
I also have a 6840 Programmable Timer, which I was attempting to hook
to the clock (E/02 at 1mhz) and divide down to something usable, but I
could not figure out how to set it up. The single chip baud rate
generators looked much simpler. If I do this, should the high and low
time of the clock be equal?
Can anyone make any suggestions on either parts or how to get the
6840 to generate an appropriate clock output? This will eventually hook
my Heathkit E-3400 microtrainer (6808) to my dumb terminal, if you have
any suggestions or experience on doing this I would like to hear it,
Thanks for any information!
Sent via Deja.com http://www.deja.com/
Before you buy.
Tom Hubin
> I'm trying to get a baud rate generator for a 6850 ACIA to drive the
> Tx and Rx clock inputs. Can anyone help with information on where to buy
> a common part or what to use? I would prefer something thats programable
> so I can change the rate on the fly.
Change with software or with jumpers or switches?
The clock needs to be 16 times the Baud Rate. Square wave is usually not
essential.
You can generate 307.2KHz with a 555 timer but I would recommend a
convenient clock divided down to 307.2KHz or something close to that.
You can use 307.2KHz to clock an 8 bit counter. This will provide 8
outputs. Each of these is usable as a 16x Baud Rate clock as follows.
16x Clock Baud Rate
307.2KHz 19200 KBaud
153.6KHz 9600 Baud
76.8KHz 4800 Baud
38.4KHz 2400 Baud
19.2KHz 1200 Baud
9.6KHz 600 Baud
4.8KHz 300 Baud
2.4KHz 150 Baud
1.2KHz 75 Baud
Jumper select an output or program a 1 of 8 multiplexor to select any
output as the Baud Rate clock.
Tom Hubin
thu...@clark.net
NO SPAM
> I'm trying to get a baud rate generator for a 6850 ACIA to drive the
> Tx and Rx clock inputs.
[snip]
The old LSI ADM-31 terminals used a COM5016 baud rate gen to drive the
6850 UART. It had two DIP switches to set the TX and RX baud rate, and
a 5.0688 MHz xtal.
Rob Barris
> Hello Paul,
>
> > I'm trying to get a baud rate generator for a 6850 ACIA to drive the
> > Tx and Rx clock inputs. Can anyone help with information on where to buy
> > a common part or what to use? I would prefer something thats programable
> > so I can change the rate on the fly.
>
> Change with software or with jumpers or switches?
>
> The clock needs to be 16 times the Baud Rate. Square wave is usually not
> essential.
>
> You can generate 307.2KHz with a 555 timer but I would recommend a
> convenient clock divided down to 307.2KHz or something close to that.
> You can use 307.2KHz to clock an 8 bit counter. This will provide 8
> outputs. Each of these is usable as a 16x Baud Rate clock as follows.
CD4060 or 74HC4060 is awesome for this. Attach a crystal and a couple
other parts (coupling caps), voila. 14 bit binary counter (not all bits
come out of the package though, lowest output divisor is /8 I think). I
use one with a separate crystal-oscillator, little pricier but very fast
to put together, one wire.
Don't forget to tie the 4060's MR (reset) pin to ground though! I left
it floating and it bit me.
Rob
ke...@ve3syb.ca
> I'm trying to get a baud rate generator for a 6850 ACIA to drive the
> Tx and Rx clock inputs. Can anyone help with information on where to buy
> a common part or what to use?