PC87309VLJ datasheet(49/192 Pages) NSC

49 / 192 page

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

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3.5.2

Result Phase Status Register 1 (ST1)

Bit 0 - Missing Address Mark

This bit indicates whether or not the Floppy Disk Con-

troller (FDC) failed to find an address mark in a data field

during a read, scan, or verify command.

0: No missing address mark.

1: Address mark missing.

Bit 0 of the result phase Status register 2 (ST2) in-

dicates the when and where the failure occurred.

See Section 3.5.3 on page 49.

Bit 1 - Drive Write Protected

When a write or format command is issued, this bit indi-

cates whether or not the selected drive is write protect-

ed, i.e., the WP signal is active.

0: Selected drive is not write protected, i.e., WP is not

active.

1: Selected drive is write protected, i.e., WP is active.

Bit 2 - Missing Data

This bit indicates whether or not data is missing for one

of the following reasons:

— Controller cannot ﬁnd the sector speciﬁed in the

command phase during the execution of a read,

write, scan, or VERIFY command. An Address Mark

(AM) was found however, so it is not a blank disk.

— Controller cannot read any address ﬁelds without a

CRC error during a READ ID command.

— Controller cannot ﬁnd starting sector during execu-

tion of READ A TRACK command.

0: Data is not missing for one of these reasons.

1: Data is missing for one of these reasons.

Bit 3 - Not Used

This bit is not used and is always 0.

Bit 4 - Overrun or Underrun

This bit indicates whether or not the FDC was serviced

by the microprocessor soon enough during a data trans-

fer in the execution phase. For read operations, this bit

indicates a data overrun. For write operations, it indi-

cates a data underrun.

0: FDC was serviced in time.

1: FDC was not serviced fast enough. Overrun or un-

derrun occurred.

Bit 5 - CRC Error

This bit indicates whether or not the FDC detected a Cy-

clic Redundancy Check (CRC) error.

0: No CRC error detected.

1: CRC error detected.

Bit 5 of the result phase Status register 2 (ST2) in-

dicates when and where the error occurred. See

Section 3.5.3.

Bit 6 - Not Used

This bit is not used and is always 0.

Bit 7 - End of Track

This bit is set to 1 when the FDC transfers the last byte

of the last sector without the TC signal becoming active.

The last sector is the End of Track sector number pro-

grammed in the command phase.

0: The FDC did not transfer the last byte of the last

sector without the TC signal becoming active.

1: The FDC transferred the last byte of the last sector

without the TC signal becoming active.

3.5.3

Result Phase Status Register 2 (ST2)

Bit 0 - Missing Address Mark Location

If the FDC cannot find the address mark of a data field

or of an address field during a read, scan, or verify com-

mand, i.e., bit 0 of ST1 is 1, this bit indicates when and

where the failure occurred.

0: The FDC failed to detect an address mark for the

address ﬁeld after two disk revolutions.

1: The FDC failed to detect an address mark for the

data ﬁeld after it found the correct address ﬁeld.

Bit 1 - Bad Track

This bit indicates whether or not the FDC detected a bad

track

0: No bad track detected.

1: Bad track detected.

The desired sector is not found. If the track number

recorded on any sector on the track is FFh and this

number is different from the track address specified

in the command phase, then there is a hard error in

IBM format.

76543210

Reset

Required

Result Phase Status

Missing Data

CRC Error

End of Track

Not Used

Overrun or Underrun

Missing Address Mark

Not Used

Drive Write Protected

76543210

Reset

Required

Result Phase Status

Scan Not Satisfied

CRC Error in Data Field

Not Used

Scan Equal Hit

Wrong Track

Missing Address

Control Mark

Bad Track

Mark Location

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