pc87317vul National Semiconductor Corporation, pc87317vul Datasheet - Page 116

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

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Command Phase
Second Command Phase Byte
Bits 1,0 - Logical Drive Select (DS1,0)
Bit 2 - Head Select (HD)
X
7
0
These bits indicate which logical drive is active. They re-
flect the values of bits 1,0 of the Digital Output Register
(DOR) described in “Bits 1,0 - Drive Select” on page 98
and of result phase status registers 0 and 3 (ST0 and
ST3) described in Sections 5.5.1 "Result Phase Status
Register 0 (ST0)" on page 107 and 5.5.4 "Result Phase
Status Register 3 (ST3)" on page 109.
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.
This bit reflects the value of bit 3 of Status Register A
(SRA) described in Section 5.3.1 "Status Register A
(SRA)" on page 96 and bit 2 of result phase status reg-
isters 0 and 3 (ST0 and ST3) described in Sections
5.5.1 "Result Phase Status Register 0 (ST0)" on page
107 and 5.5.4 "Result Phase Status Register 3 (ST3)"
on page 109, respectively.
0: HDSEL is not active, i.e., the head of the FDD se-
Media Type
2.88 MB
1.44 MB
exchanged, drive 2 is selected.
lects side 0. (Default)
360 KB
720 KB
1.2 MB
1. Gap 2 is specified in the command phase of read, write, scan, and verify commands. Although this is the
2. Gap 3 is the suggested value for the programmable GAP3 that is used in the FORMAT TRACK com-
3. The 2.88 MB diskette media is a barium ferrite media intended for use in perpendicular recording drives
MFM
X
6
recommended value, the FDC ignores this byte in read, write, scan and verify commands.
mand and is illustrated in FIGURE 5-19 "IBM, Perpendicular, and ISO Formats Supported by the FOR-
MAT TRACK Command" on page 118.
at the data rate of up to 1 Mbps.
3
X
5
0
Bytes-Per-Sector Code
Sectors per Track
Field (decimal)
Bytes in Data
Bytes in Gap 3
Data Pattern
X
4
0
512
512
512
512
512
TABLE 5-10. Typical Values for PC Compatible Diskette Media
X
3
1
HD
Bytes-Per-Sector
2
1
Code (hex)
DS1
1
0
02
02
02
02
02
DS0
0
1
116
End of Track (EOT)
Sector # (hex)
First Command Phase Byte, Opcode
Bit 6 - Modified Frequency Modulation (MFM)
Third Command Phase Byte -Bytes-Per-Sector Code
Fourth Command Phase Byte - Sectors Per Track
Bytes-Per-Sector Code (hex)
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.
1: HDSEL is active, i.e., the head of the FDD selects
This byte contains a code in hexadecimal format that in-
dicates the number of bytes in a data field.
TABLE 5-11 "Bytes per Sector Codes" shows the num-
ber of bytes in a data field for each code.
The value in this byte specifies how many sectors there
are in the track.
09
0F
09
12
24
side 1.
TABLE 5-11. Bytes per Sector Codes
00
01
02
03
04
05
06
07
Bytes in Gap 2
(hex)
2A
1B
1B
1B
1B
1
Bytes in Data Field
Bytes in Gap 3
(hex)
16384
1024
2048
4096
8192
6C
50
54
50
53
128
256
512
2