PC87338 datasheet(89/221 Pages) NSC

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Bit 4 - Equipment Check

After a RECALIBRATE command, this bit indi-

cates whether the head of the selected drive was

at track 0, i.e., whether or not TRK0 was active.

This information is used during the SENSE IN-

TERRUPT command.

0 - Head was at track 0, i.e., a TRK0 pulse oc-

curred after a RECALIBRATE command.

1 - Head was not at track 0, i.e., no TRK0 pulse

occurred after a RECALIBRATE command.

Bit 5 - SEEK End

This bit indicates whether or not a SEEK, RELA-

TIVE SEEK, or RECALIBRATE command was

completed by the controller. Used during a SENSE

INTERRUPT command.

0 - SEEK, RELATIVE SEEK, or RECALIBRATE

command not completed by the controller.

1 - SEEK, RELATIVE SEEK, or RECALIBRATE

command was completed by the controller.

Bits 7,6 - Interrupt Code (IC)

These bits indicate the reason for an interrupt.

00 - Normal termination of command.

01 - Abnormal termination of command. Execu-

tion of command was started, but was not

successfully completed.

10 - Invalid command issued. Command issued

was not recognized as a valid command.

11 - Internal drive ready status changed state

during the drive polling mode. This only oc-

curs after a hardware or software reset.

3.5.2

Result Phase Status Register 1

(ST1)

FIGURE 55. ST1 Result Phase Register Bitmap

Bit 0 - Missing Address Mark

This bit indicates whether or not the Floppy Disk

Controller (FDC) failed to find an address mark in

a data field during a read, scan, or verify com-

mand.

0 - No missing address mark.

1 - Address mark missing.

Bit 0 of the result phase Status register 2

(ST2) indicates the when and where the fail-

ure occurred. See Section 3.5.3 on page 90.

Bit 1 - Drive Write Protected

When a write or format command is issued, this bit

indicates whether or not the selected drive is write

protected, 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 Ad-

dress Mark (AM) was found however, so it is not

a blank disk.

— Controller cannot read any address fields with-

out a CRC error during a READ ID command.

— Controller cannot find starting sector during ex-

ecution 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 ser-

viced by the microprocessor soon enough during

a data transfer in the execution phase. For read

operations, this bit indicates a data overrun. For

write operations, it indicates a data underrun.

0 - FDC was serviced in time.

1 - FDC was not serviced fast enough. Overrun

or underrun occurred.

Bit 5 - CRC Error

This bit indicates whether or not the FDC detected

a Cyclic Redundancy Check (CRC) error.

0 - No CRC error detected.

1 - CRC error detected.

321

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

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