The Programmer's Guide to TRSDOS Version 6 - Tim Mann's Home ...

in this operation, an error will be returned. The Next Record Number (NRN) contained in
the FCB will be changed accordingly.
Registers Affected: AF.
Entry:
DE A pointer to the FCB for the file to skip.
Exit:
A Will contain an error return code if an error was encountered.
Z Set if the operation was successful.
7.6.84 @SLCT SVC-41
This SVC will pass a function code 1 to a disk driver. See chapter 4 for additional
information. The function will select a drive. The appropriate time delay specified in
your configuration (SYSTEM (DELAY=Y/N)) should be undertaken if the drive selection
requires it.
Registers Affected: AF [Note: DOS saves BC, IY; drivers should save any other
registers they use].
Entry:
C Contains the logical drive number (0-7).
Exit:
A Will contain an error return code if an error was encountered.
Z Set if the operation was successful.
7.6.85 @SOUND SVC-104
This SVC will interface to the sound generator if one is provided with the computer. Note
that the maskable interrupts are disabled during the duration of the tone generation. The
routine should function the same regardless of FAST/SLOW. All regs except the accumulator
are left unchanged. The Z-flag is always set on exit. For those generators capable of
multiple sounds, the linkage is as follows:
Registers Affected: AF.
Entry:
B Contains a function code packed as follows:
Bits 0-2 tone selection (0-7) with 0=highest & 7=lowest.
Bits 3-7 Contain the tone duration (0-31) with 0=short, 31=long. Short
approx 3/32 sec, long approx 3 sec.
7.6.86 @STEPI SVC-45
This SVC passes a function 5 to a disk driver. It is commonly used for specifying a stepin
controller command. See chapter 4 for more information.
Registers Affected: AF [Note: DOS saves BC, IY; drivers should save any other
registers they use].
Entry:
C Logical drive number (0-7).
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