Write a record to tape.
Write a record to the cassette. This routine is used by the higher level routines (CAS OUT CHAR, CAS OUT DIRECT and CAS OUT CLOSE) to write the header and data records that make up a tape file.
HL contains the address of the data to write.
DE contains the length of the data to write.
A contains the sync character to write at the end of the leader.
If the record was written OK:
Carry true.
A corrupt.If an error occured or the user hit escape:
Carry false.
A contains an error code.Always:
BC, DE, HL, IX corrupt.
All other registers preserved.
A data length of 0 passed to this routine is taken to mean 65536 bytes and all of memory will be written to tape. (This is unlikely to be useful).
The data to be written may lie anywhere in RAM, even underneath a ROM.
The sync character is used to distinguish header records (sync is #2C) from data records (sync is #16). Other sync characters could be used but the resulting record would require special action to be taken to read it.
The error codes returned by this routine are:
0 Break The user hit the escape key.
1 Overrun The Cassette Manager was unable to get back to writing a bit fast enough.
Because reading and writing the tape requires stringent timing considerations interrupts are disabled whilst the tape is being written (potentially a period of over 5 minutes). It would be unpleasant to have the sound chip making a noise for all this time so the Sound Manager is shut down (SOUND RESET). When writing to the tape has finished interrupts are re-enabled.
The cassette motor is started by this routine (in case it is not already on) and restored to its previous state when writing is completed.