31 Jan
2023
31 Jan
'23
3:31 a.m.
On Tue, Jan 31, 2023 at 10:56 AM Philip Belben via cctalk
<cctalk(a)classiccmp.org> wrote:
I think somebody else mentioned that one.
ZX80, ZX81, Spectrum, Acorn Acom, Acorn Electron,
BBC Micro, etc, etc.
Do you count machines like the Amstrad CPC464 which had a built-in
cassette recorder?
And don't forget the Commodore cassette port - used on the PET, VIC,
C64, ...
This blurred the line between built-in cassette drives and cassette
ports, since the built-in drive on early PETs became the separate drive
on later ones, plugging into the same port.
This didn't just switch the motor, it powered it from the computer.
When I got my first PET, I didn't have the Commodore casstte recorder
for it. So I designed a simple interface to link a normal cassette
recorder to the PET's edge connector. I used the motor drive line to
operate a relay with the contacts going to the remote socket on the
cassette unit. Since the cassette recorder I was using (a Radio Shack
CCR-82) had the +ve battery line going to the internal on-off switch,
then to the remote socket, then to the motor, I could sense the
voltage on the appropriate side of the remote socket to indicate when
the 'Play' key was pressed and use that to switch a transistor
connected to the PET's cassette switch pin.
Also unusual, I think, was that it didn't use a modem chip to generate
tones, but bit-banged them in software.
Almost all 8-bit home micros bit-banged the tones, and also decoded
them in software. I think the BBC micro (and Electron?) was the common
exception in the UK.
-tony