pc87307 National Semiconductor Corporation, pc87307 Datasheet - Page 96

• Manufacturer Part Number: pc87307
• Description: Plug And Play Compatible And Pc97 Compliant Superi/o
• Manufacturer: National Semiconductor Corporation

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5.7.10 The READ DATA Command
The READ DATA command reads logical sectors that con-
tain a normal data address mark from the selected drive and
makes the data available to the host microprocessor.
Command Phase
The READ DATA command phase bytes must specify the
following ID information for the desired sector:
After the last command phase byte is written, the controller
waits the Delay Before Processing time (see Table 5-25 on
page 106) for the selected drive. During this time, the drive
motor must be turned on by enabling the appropriate drive
and motor select disk interface output signals via the bits of
the Digital Output Register (DOR). See “Digital Output Reg-
ister (DOR), Offset 02h” on page 71.
First Command Phase Byte
Bit 5 - Skip Control (SK)
Bit 6 - Modified Frequency Modulation (MFM)
•
•
•
•
•
•
IPS
MT
7
Track number
Head number
Sector number
Bytes-per-sector code (See Table 5-11.)
End of Track (EOT) sector number. This allows the con-
troller to read multiple sectors.
The value of the data length byte is ignored and must be
set to FFh.
This controls whether or not sectors containing a delet-
ed address mark will be skipped during execution of the
READ DATA command. See Table 5-17.
0 - Do not skip sector with deleted address mark.
1 - Skip sector with deleted address mark.
This bit indicates the type of the disk drive and the data
transfer rate, and determines the format of the address
marks and the encoding scheme.
0 - FM mode, i.e., single density.
1 - MFM mode, i.e., double density.
MFM
X
6
End of Track (EOT) Sector Number
Bytes Between Sectors - Gap 3
SK
X
Data Length (Obsolete)
5
Bytes-Per-Sector Code
Sector Number
Track Number
Head Number
X
4
0
X
3
0
HD
2
1
DS1
1
1
DS0
0
0
96
Bit 7 - Multi-Track (MT)
Second Command Phase Byte
Bits 1,0 - Logical Drive Select (DS1,0)
Bit 2 - Head (HD)
Bit 7 - Implied Seek (IPS)
Third Command Phase Byte - Track Number
Fourth Command Phase Byte - Head Number
Fifth Command Phase Byte - Sector Number
Sixth Command Phase Byte - Bytes-Per-Sector Code
Seventh Command Phase Byte -
End of Track (EOT) Sector Number
This bit controls whether or not the controller continues
to side 1 of the disk after reaching the last sector of side
0.
0 - Single track. The controller stops at the last sector
1 - Multiple tracks. the controller continues to side 1 af-
These bits indicate which logical drive is active. See
“Bits 1,0 - Logical Drive Select (DS1,0)” on page 90.
00 - Drive 0 is selected. (Default)
01 - Drive 1 is selected.
10 - If four drives are supported, or drives 2 and 0 are
11 - If four drives are supported, drive 3 is selected.
This bit indicates which side of the Floppy Disk Drive
(FDD) is selected by the head. Its value is the inverse of
the HDSEL disk interface output signal.See “Bit 2 -
Head Select (HD)” on page 90.
0 - HDSEL is not active, i.e., the head of the FDD se-
1 - HDSEL is active, i.e., the FDD head selects side 1.
This bit indicates whether or not an implied seek should
be performed. See also, “Bit 5 - Implied Seek (IPS)” on
page 93.
A software reset clears this bit to its default value of 0.
0 - No implied seek operations. (Default)
1 - The controller performs seek and sense interrupt
The value in this byte specifies the number of the track
to read.
The value in this byte specifies head to use.
The value in this byte specifies the sector to read.
This byte contains a code in hexadecimal format that in-
dicates the number of bytes in a data field. Table 5-11
on page 90 indicates the number of bytes that corre-
sponds to each code.
This byte specifies the number of the sector at the End
Of the Track (EOT).
of side 0.
ter reaching the last sector of side 0.
exchanged, drive 2 is selected.
lects side 0. (Default)
operations before executing the command.