Commodore 128 Programmer's Reference Manual page 694

684 COMMODORE 128
DATA STRUCTURES
SYSTEM CONTROL BLOCK—(SCB)
The System Control Block is a 100-byte data structure. The data structure is
used as the basic communication between the various modules that make up the
CP/M Plus system. The contents of the data structure are system parameters and
variables.
y
DRIVE TABLE (DRVTBL)
PHOthrough DPHI5
A list of 16 word pointers (reverse-byte format). The first pointer (DPHO) is
drive A and the last pointer (DPH15) is drive P. The pointers point to the XDPH
for that disk drive. Any drive that is not in the system has its pointers set to
zero.
EXTENDED DISK PARAMETER HEADER (XDPH)
(NORMAL DPH WITH A HEADER)
WRT READ LOGIN
16b
-10
16b
-8
16b
-6
INTT
16b
-A
TYPE UNIT XLT
8b
-2
8b
-1
16b
0
-0-
72b
2
MF
8b
11
DPB CSV ALV DIRBCB DTABCB HASH HBANK
16b 16b 16b
12 14 16
16b
18
16b
20
16b
22
8b
24
WRT Contains the address of the sector write routine for this drive.
READ Contains the address of the sector read routine for this drive.
LOGIN Contains the address of the login routine for this drive.
INIT Contains the address of the first time initialization routine for this drive.
TYPE This byte is used by the BIOS to keep track of density and media type.
UNIT Contains the drive number relative to the disk controller.
XLT Contains the address of the sector translation table or zero if none.
-0- BDOS scratch area (9 bytes).
MF Media flag cleared to zero if disk logged in. BIOS sets to OFFH if media
has changed.
DPB Contains a pointer to the current DPB that describes the current media type.
CSV Contains a pointer to directory checksum area (one per disk drive).
ALV Contains a pointer to allocation vector area (one per disk drive).
DIRBCB Contains a pointer to a single directory Buffer Ciontrol Block (BCB).
DTSBCB Contains a pointer to a single data Buffer Control Block (BCB).
HASH Contains a pointer to an optional directory hashing table (FFFFH is
not used).
HBANK Contains a bank number of the directory hashing table.
u
U
u
ii
1
L
U
U