PC87309VLJ datasheet(53/192 Pages) NSC

53 / 192 page

The Floppy Disk Controller (FDC) (Logical Device 0)

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3.7

COMMAND SET

The first command byte for each command in the FDC com-

mand set is the opcode byte. The FDC uses this byte to de-

termine how many command bytes to expect.

If an invalid command byte is issued to the controller, it im-

mediately enters the result phase and the status is 80h, sig-

nifying an invalid command.

TABLE 3-8 shows the FDC commands in alphabetical order

with the opcode, i.e., the first command byte, for each.

In this table:

MT is a multi-track enable bit (See “Bit 7 - Multi-Track

(MT)” on page 64.)

MFM is a modiﬁed frequency modulation parameter

(See “Bit 6 - Modiﬁed Frequency Modulation (MFM)”

on page 57.)

SK is a skip control bit. (See “Bit 5 - Skip Control (SK)”

on page 64.)

Section 3.7.1 explains some symbols and abbreviations

you will encounter in the descriptions of the commands.

All phases of each command are described in detail, start-

ing with Section 3.7.2 on page 55, with bitmaps of each byte

in each phase.

Only named bits and fields are described in detail. When a

bitmap shows a value (0 or 1) for a bit, that bit must have

that value and is not described.

TABLE 3-8. FDC Command Set Summary

Command

Opcode

4 3210

CONFIGURE

1 0 0 1 1

DUMPREG

0 1 1 1 0

FORMAT TRACK

MFM

0 1 1 0 1

INVALID

Invalid Opcode

LOCK

1 0 1 0 0

MODE

0 0 0 0 1

NSC

1 1000

PERPENDICULAR

MODE

1 0010

READ DATA

MFM

0 0 1 1 0

READ DELETED

DATA

MFM

0 1 1 0 0

READ ID

MFM

0 1 0 1 0

READ TRACK

MFM

0 0 0 1 0

RECALIBRATE

0 0 1 1 1

RELATIVE SEEK

DIR

0 1 1 1 1

SCAN EQUAL

MFM

1 0 0 0 1

SCAN HIGH OR

EQUAL

MFM

1 1 1 0 1

SCAN LOW OR

EQUAL

MFM

1 1 0 0 1

SEEK

0 1 1 1 1

SENSE DRIVE

STATUS

0 0100

SENSE INTERRUPT

0 1 0 0 0

SET TRACK

0 0 0 0 1

SPECIFY

0 0 0 1 1

VERIFY

MFM

1 0 1 1 0

VERSION

1 0 0 0 0

WRITE DATA

MFM

0 0 1 0 1

WRITE DELETED

DATA

MFM

0 1 0 0 1

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