Atari 400 Technical Reference Manual page 58

7
o
+-+-+-+-+-+-+-+-+
AUX2
:C:
+-+-+-+-+-+-+-+-+
Where: C
=
1 indicates that the cassette is to be read/written without
stop/start between records (continuous made).
Opening the cassette
for
input generates a single audible tone, as a
prompt for
~ou
to
verif~
that the cassette player is set up
for reading (power ani Serial Bus cable connected; tape cued to start
of file; and PLAY button depressed). When the cassette is ready,
you can press any ke~board key (except [BREAK]) to initiate tape
reading.
Opening the cassette
for
output generates two closely spaced audible
tones, as a prompt for you to verify that the cassette player
is set up for writing (as above, plus RECORD button depressed). When
the cassette is ready, you can press any keyboard key (except
[BREAK]) to begin tape writing. There is no way for the computer to
verify that the RECORD Qr PLAY button is depressed. It is possible for
the file nat to be written, with no immediate indication of this fact.
There is a potential problem with the cassette in that when the
cassette is opened·for writing, the motor keeps running until the
first record (128 data bytes) is written. If 128 data bytes are
written or the cassette is closed within about 30 seconds of the OPEN,
and no other serial bus I/O is performed, then there is no problem.
However, if those conditions are not met, some noise will be written
to the tape prior to the first record and an
error
will occur when
that tape file is read later. If lengthy delays are anticipated
between the time the cassette file is opened and the time that the
first cassette record (128 data bytes) is written, then a dummy record
should be written as part of the file; typically 128 bytes of some
innocuous data would be written, such as all zeros, all $FFs, or all
blanks ($20).
The system sometimes emits whistling noises after cassette I/O has
occurred. The sound can be eliminated by storing $03 to SKCTL [D20Fl,
thus bring POKEY out of the two-tone (FSK) mode.
CLOSE
The CLOSE of a tape read· stops the cassette motor.
The CLOSE of a tape write does the following:
Writes any remaining user data in the buffer to tape.
Writes aft end-of-file record.
Stops the cassette motor.
OPERATING SYSTEM CQ16555 -- Section 5
73