Check to see if unit 1 is present
Function AddressDescription
DD_ASK_1 017BCheck to see if unit 1 is present


Check to see if unit 1 is present. BASIC holds this information in bit 5 of the FLAGS3 system variable.

Turn motor on.

Fetch drive status.

If unit 1 is not-ready and write-protected, then unit 1 is missing. Start motor off timeout.

Note that this routine can be fooled by disks which are almost, but not quite, inserted in the drive.

This routine assumes that when a disk is not in the drive, then write-protect is true. This is indeed the case for 3 inch and 8 inch disk drives, but is not the case for 5 1/4 inch disk drives.

Entry Parameters


Exit Parameters

If unit 1 present:
Carry true
Carry false
A BC DE HL IX corrupt, all other registers preserved.
Last modified November 24, 2021: Low level operations (11836cf)