Tandy 600 Programmer's Reference Manual page 155

INT 53h,
Function 4
-
Write Block
Entry:
AH
=
4
(function
code)
AL
=
block-type
CX
=
byte
count (does not include block-type)
DX-
segment
address
of
data
buffer
BX
=
offset
address
of
data
buffer
Exit:
AL=
Standard
BIOS
error
codes
This
routine
should perform the following steps:
1.
Start
the
motor and
delay
until
the
motor
is
at
full
speed. (The length of the
delay
required
depends on
the characteristics of
the cassette
drive.
For inexpensive cassette recorders a
delay
of
one-half
second
is
usually
adequate.)
2.
Write the
OEM
specified block-header.
3.
Write the bfock-type
byte.
4.
Write the specified
number
of
bytes from the specified
buffer.
5.
Write the
OEM
specified
block-trailer.
6.
Turn the
motor
off
and
return.
INT 53h,
Function
5
-
Read
Block
Entry:
AH
=
5 (function
code)
CX=buffer
length
DX
=
segment address
of
data
buffer
BX
=
offset
address
of
data
buffer
Exit:
AL=
Standard BIOS
error
code
AH =
block-type (read
from tape)
CX
= number
of
bytes
of
data placed
in
the buffer
This routine
should perform
the following steps:
1.
Start
the
motor
and
delay
until
the
motor
is
at
full
speed. (The
length of
the
delay required
depends on
the characteristics
of
the cassette
drive.
For inexpensive cassette recorders a
delay
of
one-half second
is
usually adequate.)
2.
Read
the
OEM
specified block-header.
3.
Read
the block-type byte.
4.
Read
the data
into
the
buffer,
checking
for
buffer overflow.
5.
Read
the
OEM
specified block-trailer,
and
verify
the
checksum.
6.
Turn the
motor
off
and
return.
150