Datasheet

Set Features
This command allows the host to alter the card's internal clock, choosing from three speeds to optimize performance
and power. Table 3 on page 21shows the valid data which may be set in the Feature Register by the Host. All other
values are invalid and will cause the ABRT (Command Aborted) bit to be set in the Error Register and the command
to terminate. A feature number of 97h specifies that the FCA card’s internal clock is to be set according to the
code in the Sector Count register. The remaining valid values are essentially NOPs, simply returning command
completed status.
Set Features Command Issued by Host
Task File Register 7 6 5 4 3 2 1 0
COMMAND EFh
DRIVE/HEAD nu nu nu D nu
CYLINDER HI nu
CYLINDER LOW nu
SECTOR START nu
SECTOR COUNT If Feature Number = 97h, then specifies the card’s internal clock according to Table 4 below
FEATURES Feature Number. Refer to Table 3.
Command Block specified upon completion/termination of Set Features command (EFh)
Task File Register 7 6 5 4 3 2 1 0
BSY DRDY DWF DSC DRQ CORR IDX ERR
STATUS 0 1 0 1 V V 0 V
DRIVE/HEAD na na na na na
CYLINDER HI na
CYLINDER LOW na
SECTOR na
SECTOR COUNT na
BBK UNC MC IDNF MCR ABRT TK0NF AMNF
ERROR 0 0 0 0 0 V 0 0
Table 3. Description of Valid Feature Numbers
Code Description
97h set clock speed per contents of Sector Count Register
44h valid; no operation (for backward compatibility)
55h valid; no operation (for backward compatibility)
69h valid; no operation (for backward compatibility)
96h valid; no operation (for backward compatibility)
AAh valid; no operation (for backward compatibility)
BBh valid; no operation (for backward compatibility)
Table 4. Sector Count Code specifies internal clock rate
Code Description
00h Divide by 4
0Ah Divide by 2
0Bh Divide by 2
0Eh Divide by 1
0Fh Divide by 1