PC87307VUL National Semiconductor, PC87307VUL Datasheet - Page 90

• Manufacturer Part Number: PC87307VUL
• Description: PC87307/PC97307 Plug and Play Compatible and PC97 Compliant SuperI/O
• Manufacturer: National Semiconductor

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First Command Phase Byte, Opcode
Bit 6 - Modified Frequency Modulation (MFM)
Second Command Phase Byte
Bits 1,0 - Logical Drive Select (DS1,0)
Bit 2 - Head Select (HD)
Third Command Phase Byte -Bytes-Per-Sector Code
Media Type
2.88 MB
1.44 MB
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.
These bits indicate which logical drive is active. They re-
flect the values of bits 1,0 of the Digital Output Register
(DOR) described on page 72 and of result phase status
registers 0 and 3 (ST0 and ST3) described on pages 81
and 83, respectively.
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 on page 70 and bit 2 of result phase
status registers 0 and 3 (ST0 and ST3) described on
pages 81 and 83, respectively.
0 - HDSEL is not active, i.e., the head of the FDD se-
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 shows the number of bytes in a data field for
each code.
360 KB
720 KB
1.2 MB
a. Gap 2 is specified in the command phase of read, write, scan, and verify commands. Although this is the rec-
b. Gap 3 is the suggested value for the programmable GAP3 that is used in the FORMAT TRACK command and
c. The 2.88 MB diskette media is a barium ferrite media intended for use in perpendicular recording drives at the
exchanged, drive 2 is selected.
lects side 0. (Default)
side 1.
ommended value, the FDC ignores this byte in read, write, scan and verify commands.
is illustrated in Figure 5-20.
data rate of up to 1 Mbps.
c
Field (decimal)
Bytes in Data
512
512
512
512
512
TABLE 5-10. Typical Values for PC Compatible Diskette Media
Bytes-Per-Sector
Code (hex)
02
02
02
02
02
End of Track (EOT)
90
Sector # (hex)
Fourth Command Phase Byte - Sectors Per Track
Fifth Command Phase Byte - Bytes in Gap 3
Sixth Command Phase Byte - Data Pattern
Execution Phase
The system transfers four ID bytes (track number, head
number, sector number and bytes-per-sector code) per sec-
tor to the Floppy Disk Controller (FDC) in either a DMA or a
non-DMA mode. Section 5.4.2 on page 78 describes these
modes.
The entire track is formatted. The data block in the data field
of each sector is filled with the data pattern byte.
Only the first three status bytes in this phase are significant.
Bytes-Per-Sector Code (hex)
The value in this byte specifies how many sectors there
are in the track.
The number of bytes in gap 3 is programmable. The
number to program for Gap 3 depends on the data
transfer rate and the type of the disk drive. Table 5-12
shows some typical values to use for Gap 3.
Figure 5-20 illustrates the track format for each of the
formats recognized by the FORMAT TRACK command.
This byte contains the contents of the data field.
09
0F
09
12
24
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
Bytes in Data Field
a
Bytes in Gap 3
16384
1024
2048
4096
8192
128
256
512
(hex)
6C
50
54
50
53
b