SMCXXXAF Datasheet, PDF (65/82 Pages) Numonyx B.V – 32 Mbyte, 64 Mbyte, 128 Mbyte, 256 Mbyte and 512 Mbyte 3.3 V / 5 V supply CompactFlash™ card

SMCxxxAF
CF-ATA command description
9.15
Seek command (7Xh)
This command is effectively a NOP command to the card although it does perform a range
check of cylinder and head or LBA address and returns an error if the address is out of
range. Table 64 shows the Seek command byte sequence.
Table 64. Seek
Bit
7
6
5
4
3
2
1
0
Command (7)
7Xh
C/D/H (6)
Cyl High (5)
1
LBA
1
Drive
Head (LBA 27-24)
Cylinder High (LBA 23-16)
Cyl Low (4)
Cylinder Low (LBA 15-8)
Sect Num (3)
X (LBA 7-0)
Sect Cnt (2)
X
Feature (1)
X
9.16
Set Features command (EFh)
This command is used by the host to establish or select certain features. Table 65 shows the
Set Features command byte sequence. Table 66 defines all features that are supported.
Features 01h and 81h are used to enable and clear 8 bit data transfer modes in True IDE
mode. If the 01h Feature command is issued all data transfers will occur on the low order
D7D0 data bus and the –IOIS16 signal will not be asserted for data register accesses.
Feature 03h allows the host to select the PIO transfer mode by specifying a value in the
Sector Count register (see Table 67 for values). The upper 5 bits define the type of transfer
and the low order 3 bits encode the mode value. One PIO mode should be selected at all
times. The host may change the selected mode by issuing the Set Features command.
Feature code 9Ah enables the host to configure the card to best meet the host system's
power requirements. The host sets a value in the Sector Count register that is equal to one-
fourth of the desired maximum average current (in mA) that the card should consume. For
example, if the Sector Count register were set to 6, the card would be configured to provide
the best possible performance without exceeding 24 mA. Upon completion of the command,
the card responds to the host with the range of values supported by the card. The minimum
value is set in the Cylinder Low register, and the maximum value is set in the Cylinder Hi
register. The default value, after a power on reset, is to operate at the highest performance
and therefore the highest current mode.
The card will accept values outside this programmable range, but will operate at either the
lowest power or highest performance as appropriate.
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