PC97338VLJ datasheet(105/221 Pages) NSC

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Second Command Phase Byte

A hardware reset clears all the bits to zero (conven-

tional mode for all drives). PERPENDICULAR MODE

command bits may be written at any time.

The settings of bits 1 and 0 in this byte override the

logical drive configuration set by bits 5 through 2. If

bits 1 and 0 are both 0, bits 5 through 2 configure the

logical disk drives as conventional or perpendicular.

Otherwise, bits 2 and 0 configure them. See Table 50.

Bits 1,0 - Group Drive Mode Configuration (GDC)

These bits configure all the logical disk drives as

conventional or perpendicular. If the Overwrite bit

(OW, bit 7) is 0, this setting may be overridden by

bits 5-2.

It is not necessary to issue the FORMAT TRACK

command if all drives are conventional.

These bits are cleared to 0 by a software reset.

00 - Conventional. (Default)

01 - Perpendicular. (500 Kbps)

10 - Conventional.

11 - Perpendicular. (1 or 2 Mbps)

Bits 5-2 -Drive 3-0 Mode Configuration (DC3-0)

If bits 1,0 are both 0, and bit 7 is 1, these bits con-

figure logical drives 3-0 as conventional or perpen-

dicular. Bits 5-2 (DC3–0) correspond to logical

drives 3-0, respectively.

These bits are not affected by a software reset.

0 - Conventional drive. (Default)

It is not necessary to issue the FORMAT

TRACK command for conventional drives.

1 - Perpendicular drive.

Bit 7 - Overwrite (OW)

This bit enables or disables changes in the mode

of the logical drives by bits 5-2.

0 - Changes in mode of logical drives via bits 5-2

are ignored. (Default)

1 - Changes enabled.

Execution Phase

Internal registers are written.

Result Phase

None.

3.6.10 The READ DATA Command

The READ DATA command reads logical sectors that

contain a normal data address mark from the selected

drive and makes the data available to the host micro-

processor.

Command Phase

The READ DATA command phase bytes must specify

the following ID information for the desired sector:

• Track number

• Head number

• Sector number

• Bytes-per-sector code (See Table 44.)

• End of Track (EOT) sector number. This allows the

controller to read multiple sectors.

• The value of the data length byte is ignored and

must be set to FF (hex).

After the last command phase byte is written, the con-

troller waits the Delay Before Processing time (see

Table 59 on page 117) for the selected drive. During

this time, the drive motor must be turned on by en-

abling the appropriate drive and motor select disk in-

terface output signals via the bits of the Digital Output

Offset 010” on page 77.

First Command Phase Byte

Bit 5 - Skip Control (SK)

This controls whether or not sectors containing a

deleted address mark will be skipped during exe-

cution of the READ DATA command. See Table

51.

0 - Do not skip sector with deleted address mark.

1 - Skip sector with deleted address mark.

7654

3210

MFM

0110

IPS

DS1

DS0

Track Number

Head Number

Sector Number

Bytes-Per-Sector Code

End of Track (EOT) Sector Number

Bytes Between Sectors - Gap 3

Data Length (Obsolete)

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