The Amstrad CPC Firmware Guide
63
The Cassette/AMSDOS manager
NOTE: Some of these routines are only applicable to the cassette manager; where a disc version
exists it is indicated by an asterisk (*) next to the command name. These disc version jumpblocks are
automatically installed by the Operating System on switch on.
&BC65 CAS INITIALISE
Action Initialises the cassette manager
Entry No entry conditions
Exit AF, BC, DE and HL are corrupt, and all the other registers are preserved
Notes Both read and write streams are closed; tape messages are switched on; the default speed is reselected
&BC68 CAS SET SPEED
Action Sets the speed at which the cassette manager saves programs
Entry HL holds the length of `half a zero' bit, and A contains the amount of precompensation
Exit AF and HL are corrupt
Notes
The value in HL is the length of time that half a zero bit is written as; a one bit is twice the length of a
zero bit; the default values (ie SPEED WRITE 0) are 333 microseconds (HL) and 25 microseconds (A)
for SPEED WRITE 1, the values are given as 107 microseconds and 50 microseconds respectiveIy
&BC6B CAS NOISY
Action Enables or disables the display of cassette handling messages
Entry To enable the messages then A must be 0, otherwise the messages are disabled
Exit AF is corrupt, and all other registers are preserved
&BC6E CAS START MOTOR
Action Switches on the tape motor
Entry No entry conditions
Exit
If the motor operates properly then Carry is true; if ESC was pressed then Carry is false; in either case,
A contains the motor's previous state, tbe flags are corrupt, and all others are preserved
&BC71 CAS STOP MOTOR
Action Switches off the tape motor
Entry No entry conditions
Exit
If the motor turns off then Carry is true; if ESC was pressed then Carry is false; in both cases, A holds
tbe motor's previous state, the other flags are corrupt, all others are preserved
&BC74 CAS RESTORE MOTOR
Action Resets the tape motor to its previous state
Entry A contains the previous state of the motor (eg from CAS START MOTOR or CAS STOP MOTOR)
Exit
If the motor operates properly then Carry is true; if ESC was pressed then Carry is false; in all cases, A
and the other flags are corrupt and all others are preserved
&BC77 *CAS IN OPEN
Action Opens an input buffer and reads the first block of the file
Entry
B contains the length of the filename, HL contains the filename's address, and DE contains the address
of the 2K buffer to use for reading the file
Exit
If the file was opened successfully, then Carry is true, Zero is false, HL holds the address of a buffer
contauling the file header data, DE holds the address of the destination for the file, BC holds the file
length, and A holds the file type; if the read stream is already open then Carry and Zero are false, A
contains an error nurnber (664/6128 only) and BC, DE and HL are corrupt; if ESC was pressed by the
user, then Carry is false, Zero is true, A holds an error number (664/6128 only) and BC, DE and HL are
corrupt; in all cases, IX and the other flags are corrupt, and the others are preserved
(16 pages)
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