16 May
2001
16 May
'01
9:51 p.m.
> On Wednesday 16 May 2001 14:05, Sellam Ismail hit
his keyboard with a hammer
> and this was the result:
> > You're assuming he won't do something clever such as add an electronic
> > counter so he can fast forward to just before the desired block?
> I was planing on this. I will have a block of
sound at the start of the tape,
> that will indicate what is 1 second for this recorder. This will calibrate it
> to be able to seek the second of the tape it wants. It will then read in the
> FAT and seek the file directly.
Remember that the tape speed is not constant (assuming
constant speed
motors) in fast forward or rewind mode. Because the diameter of the
spools changes as tape winds on/off them.
Some people have tried clever tricks where they put
some kind of
tachometer (slotted disk + optoswitch, or tachogenerator) on each spool.
By measuring the speed of both of them, they can work out roughly where
they are on the tape, and also, by counting _both_ sets of tacho pulses
it's possible to do a reasonably accurate seek. It's still generally
necessary to format the tape (as in writing down block headers and dummy
data) when you first use a new blank tape, and then seeking by going to
approximately the right place and then reading a few blocks to get to the
right one.
Also this would almost need a seperate CPU for tape control.
Otherwise the Computer would be more like a ZX81 - with all
the fine tuning needed for timing your programm code with the
tape hardware.
Although it sounds like a fun project, I would skip this and
go for a simple solution.
Gruss
H.
--
VCF Europa 3.0 am 27./28. April 2002 in Muenchen
http://www.vcfe.org/