pc87317vul National Semiconductor Corporation, pc87317vul Datasheet - Page 129

• Manufacturer Part Number: pc87317vul
• Description: Pc87317vul/pc97317vul Superi/o Plug And Play Compatible With Acpi Compliant Controller/extender
• Manufacturer: National Semiconductor Corporation

TABLE 5-21 "The Effect of Scan Commands on the ST2
Register" shows how all the scan commands affect bits 3,2
of the Status 2 (ST2) result phase register. See Section
5.5.3 "Result Phase Status Register 2 (ST2)" on page 108.
TABLE 5-21. The Effect of Scan Commands on the ST2
5.7.17 The SEEK Command
The SEEK command issues pulses of the STEP signal to
the selected drive, to move it in or out until the desired track
number is reached.
Software should ensure that the SEEK command is issued
for only one drive at a time. This is because the drives are
actually selected via the Digital Output Register (DOR),
which can only select one drive at a time. See Section 5.3.3
"Digital Output Register (DOR)" on page 97.
No command, except a SENSE INTERRUPT command,
should be issued while a SEEK command is in progress.
Command Phase
When bit 2 of the second command phase byte (ETR) in the
MODE command is set to 1, the track number is stored as
a 12-bit value. See “Bit 0 - Extended Track Range (ETR)”
on page 119.
In this case, a fourth command byte should be written in the
command phase to hold the Most Significant Nibble (MSN),
i.e., the four most significant bits, of the number of the track
to seek. Otherwise (ETR bit in MODE is 0), this command
phase byte is not required. and, only three command bytes
should be written.
After the last command byte is issued, the Drive Busy bit for
the selected drive is set in the Main Status Register (MSR).
See bits 3-0 in Section 5.3.5 "Main Status Register (MSR)"
on page 100.
The controller waits the Delay Before Processing time (see
TABLE 5-25 "Constant Multipliers for Delay Before Pro-
cessing Factor and Delay Ranges" on page 132) for the se-
SCAN HIGH
SCAN LOW
OR EQUAL
OR EQUAL
Command
MSN of Track # to Seek
X
7
0
EQUAL
SCAN
X
6
0
Bit 3 - Scan
Number of Track to Seek
Satisfied
X
5
0
Result Phase Status
Register 2 (ST2)
1
0
1
0
0
1
0
0
Register
X
4
0
Not Satisfied
Bit 2 - Scan
X
3
1
0
1
0
0
1
0
0
1
HD
2
1
DS1
Condition
Disk = P
Disk
Disk = P
Disk < P
Disk > P
Disk = P
Disk > P
Disk < P
1
1
DS0
0
1
P
129
lected drive, before issuing the first STEP pulse. After
waiting the Delay Before Processing time, the controller be-
comes idle. See Section 5.4.4 "Idle Phase" on page 106.
Second Command Phase Byte
Third Command Phase Byte, Number of Track to Seek
Fourth Command Phase Byte,
Bits 7-4 - MSN of Track Number
Execution Phase
During the execution phase of the SEEK command, the
track number to seek to is compared with the present track
number. The controller determines how many STEP pulses
to issue and the DIR disk interface output signal indicates
which direction the head should move.
The SEEK command issues step pulses while the controller
is in the drive polling phase. The step pulse rate is deter-
mined by the value programmed in the second command
phase byte of the SPECIFY command.
An interrupt is generated one step pulse period after the last
step pulse is issued. A SENSE INTERRUPT command
should be issued to determine the cause of the interrupt.
Result Phase
5.7.18 The SENSE DRIVE STATUS Command
The SENSE DRIVE STATUS command indicates which
drive and which head are selected, whether or not the head
is at track 0 and whether or not the track is write protected
in result phase Status register 3 (ST3). See Section 5.5.4
"Result Phase Status Register 3 (ST3)" on page 109. This
command does not generate an interrupt.
Command Phase
See READ DATA command for a description of these bits.
Execution Phase
Disk drive status information is detected and reported.
Result Phase
See Section 5.5.4 "Result Phase Status Register 3 (ST3)"
on page 109.
X
7
0
7
See READ DATA command for a description of these bits.
The value in this byte is the number of the track to seek.
If the track number is stored as a 12-bit value, these bits
contain the Most Significant Nibble (MSN), i.e., the four
most significant bits, of the number of the track to seek.
Otherwise (the ETR bit in the MODE command is 0), this
command phase byte is not required.
None.
X
6
0
6
Result Phase Status Register 3 (ST3)
X
5
0
5
X
4
0
4
X
3
0
3
HD
2
1
2
DS1
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1
0
1
DS0
0
0
0