Commodore 128 Programmer's Reference Manual page 689

AUXOUT
Bank: 0 or 1
Input:
C = ASCII Character to send to AUX device
Output: None
Function:
Sends the character in C to ALL devices that are currently
assigned to the AUXOUT device. It waits for all assigned devices
to accept a character before exiting.
AUXIN
Bank: 0 or 1
Input:
None
Output:
A = ASCII character from AUX device
Function:
Reads a character from any ONE of the assigned AUXIN devices.
A scan of each assigned device is done until an input character
is found. The character is returned in the A register.
HOME
Bank: 0
Input: None
Output: None
Function:
Homes the head on the currently selected disk drive. This
function sets the current track to 0 and does not move the head
of the disk.
SELDSK
Bank: 0
Input: C = Disk Drive (0-15) (A = 0)
E = Initial Select Flag (LSB)
Output: HL = Address of Disk Parameter Header (DPH) if drive exists.
HL = 000H if drive does not exist.
Function:
Selects the disk drive whose address is in C as the current drive
for all further disk operations. If the LSB of the E register is a
zero, then this is the first logging of this disk. The disk type
(C64 CP/M, MFM or C128 CP/M) is checked and the DPB
parameters adjusted for the diskette currently in the drive.
10 SETTRK
Bank: 0
Input: BC = Track number
Output: None
Function:
Register pair BC contains the track number to be used in the
subsequent disk access. This value is saved.
11 SETSEC
Bank: 0
Input: BC = Sector number
Output: None
Function: Register pair BC contains the sector number to be used in the
subsequent disk access. This value is saved. The value in BC
is the value returned by the sector translation routine (in HL).
APPENDIXES 679