System information

The DISKS macro generates n DPHS, starting at the DPH table address DPBASE generated by

the macro. Each disk header block contains sixteen bytes, as described above, and correspond

one-for-one to each of the defined drives. In the four-drive standard system, for example, the

DISKS macro generates a table of the form:

DPBASE EQU $

DPEO: DW XLT0,0000H,0000H,0000H,DIRBUF,DPB0,CSV0,ALV0

DPE1: DW XLT0,0000H,0000H,0000H,DIRBUF,DPB0,CSV1,ALV1

DPE2: DW XLT0,0000H,0000H,0000H,DIRBUF,DPB0,CSV2,ALV2

DPE3: DW XLT0,0000H,0000H,0000H,DIRBUF,DPB0,CSV3,ALV3

where the DPH labels are included for reference purposes to show the beginning table addresses

for each drive 0 through 3. The values contained within the DPH are described in detail in the

previous section. The check and allocation vector addresses are generated by the ENDEF macro

in the RAM area following the BIOS code and tables.

Note that if the skf (skew factor) parameter is omitted, or equal to 0, the translation table is

omitted and a 0000H value is inserted in the XLT position of the DPH for the disk. In a

subsequent call to perform the logical-to-physical translation, SECTRAN receives a translation

table address of DE = 0000H and simply returns the original logical sector from BC in the HL

A translate table is constructed when the skf parameter is present, and the (nonzero) table address

is placed into the corresponding DPHS. The following, for example, is constructed when the

standard skew factor skf = 6 is specified in the DISKDEF macro call:

XLT0: DB 1,7,13,19,25,5,11,17,23,3,9,15,21

DB 2,8,14,20,26,6,12,18,24,4,10,16,22

6.11 The DISKDEF Macro Library CP/M Operating System Manual

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