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Cassette Baud...

PostPosted: Tue Jul 17, 2012 9:10 am
by Rink
Quick question, but I've had difficulty finding the information from Google: what's the (approximate is fine) baud rate of the Dragon 32's cassette interface?

Cheers.

Re: Cassette Baud...

PostPosted: Tue Jul 17, 2012 11:19 am
by Dragonizer
According to Dragon User Magazine Issue September 1985, page 19 it's 1500 Baud.

Re: Cassette Baud...

PostPosted: Tue Jul 17, 2012 4:36 pm
by Rink
Really? Seems slower than that to me. :)

Cheers mate. Much appreciated.

Re: Cassette Baud...

PostPosted: Tue Jul 17, 2012 5:15 pm
by Sarah
The symbol rate is variable, since it takes only half as long to transmit a "1" bit compared to a "0" bit. I wonder if the quoted baud rate accounts for this (perhaps being an average), or whether it even makes sense to have a single value rather than a range?

Re: Cassette Baud...

PostPosted: Tue Jul 17, 2012 6:06 pm
by prime
Sarah wrote:The symbol rate is variable, since it takes only half as long to transmit a "1" bit compared to a "0" bit. I wonder if the quoted baud rate accounts for this (perhaps being an average), or whether it even makes sense to have a single value rather than a range?


Really? I always thought it was 1 cycle of 1200 or 2 cycles of 2400 for each bit so that the bit time is the same.

Cheers.

Phill.

Re: Cassette Baud...

PostPosted: Tue Jul 17, 2012 8:59 pm
by zephyr
This is fully explained on page 213 of Inside The Dragon.

Re: Cassette Baud...

PostPosted: Tue Jul 17, 2012 11:13 pm
by Sarah
prime wrote:
Sarah wrote:The symbol rate is variable, since it takes only half as long to transmit a "1" bit compared to a "0" bit. I wonder if the quoted baud rate accounts for this (perhaps being an average), or whether it even makes sense to have a single value rather than a range?


Really?


Yep!

Try filling a large area of memory with $FF and then an equal amount with $00; it's easy to hear that the $FF blocks are half the length of the $00 blocks!

zephyr wrote:This is fully explained on page 213 of Inside The Dragon.


Well spotted...

"the effective data transfer rate from Dragon to cassette recorder is 1800 bits/second as, on average, there will be an equal number of ones and zeros recorded for a program or data file"


Presumably Brian Cadge gives a lower approximate figure in his article to adjust for overheads.