System information

Table 6-5. (continued)
Entry Point Function
WRITE Data is written from the currently selected DMA address to the currently
selected drive, track, and sector. For floppy disks, the data should be
marked as nondeleted data to maintain compatibility with other CP/M
systems. The error codes given in the READ command are returned in
register A, with error recovery attempts as described above.
LISTST You return the ready status of the list device used by the DESPOOL
program to improve console response during its operation. The value 00 is
returned in A if the list device is not ready to accept a character and 0FFH
if a character can be sent to the printer. A 00 value should be returned if
LIST status is not implemented.
SECTRAN Logical-to-physical sector translation is performed to improve the overall
response of CP/M. Standard CP/M systems are shipped with a skew factor
of 6, where six physical sectors are skipped between each logical read
operation. This skew factor allows enough time between sectors for most
programs to load their buffers without missing the next sector. In
particular computer systems that use fast processors, memory, and disk
subsystems, the skew factor might be changed to improve overall
response. However, the user should maintain a single-density
IBM-compatible version of CP/M for information transfer into and out
of the computer system, using a skew factor of 6.
In general, SECTRAN receives a logical sector number relative to zero in
BC and a translate table address in DE. The sector number is used as an
index into the translate table, with the resulting physical sector number in
HL. For standard systems, the table and indexing code is provided in the
CBIOS and need not be changed.
6.6 BIOS Entry Points CP/M Operating System Manual
6-24