PC87307 datasheet(82/218 Pages) NSC

82 / 218 page

The Digital Floppy Disk Controller (FDC) (Logical Device 3)

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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 5.5.3.

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.

5.5.3

Result Phase Status Register 2 (ST2)

FIGURE 5-18. ST2 Result Phase Register Bitmap

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.

Bit 2 - Scan Not Satisﬁed

This bit indicates whether or not the value of the data

byte from the microprocessor meets any of the condi-

tions specified by the scan command used.

“The SCAN EQUAL, the SCAN LOW OR EQUAL and

the SCAN HIGH OR EQUAL Commands” on page 101

and Table 5-21 describes the conditions.

0 - The data byte from the microprocessor meets at

least one of the conditions speciﬁed.

1 - The data byte from the microprocessor does not

meet any of the conditions speciﬁed.

Bit 3 - Scan Satisﬁed

This bit indicates whether or not the value of the data

byte from the microprocessor was equal to a byte on the

floppy disk during any scan command.

0 - No equal byte was found.

1 - A byte whose value is equal to the byte from the mi-

croprocessor was found on the ﬂoppy disk.

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

PC87307 Datasheet(PDF) 82 Page - National Semiconductor (TI)

PC87307 Datasheet(HTML) 82 Page - National Semiconductor (TI)

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