PC87306 datasheet(33/110 Pages) NSC

33 / 110 page

30 FDC Register Description (Continued)

321 Status Register 0 (ST0)

DESC

HDS

DS1

DS0

RESET

COND

D7 6

Interrupt Code

00 e Normal Termination of Command

01 e Abnormal Termination of Command Execu-

tion of command was started but was not

successfully completed

10 e Invalid Command Issued Command issued

was not recognized as a valid command

11 e Internal drive ready status changed state dur-

ing the drive polling mode Only occurs after

a hardware or software reset

Seek End

Seek Relative Seek or Recalibrate

command completed by the controller (Used during

a Sense Interrupt command)

Equipment Check

After a Recalibrate command

Track 0 signal failed to occur (Used during Sense

Interrupt command)

Not Used

Always 0

Head Select

Indicates the active high status of the

HDSEL pin at the end of the Execution Phase

D1 0

Drive Select 10

These two binary encoded bits

indicate the logical drive selected at the end of the

Execution Phase

00 e Drive 0 selected

01 e Drive 1 selected

10 e Drive 2 selected

11 e Drive 3 selected

322 Status Register 1 (ST1)

DESC

RESET

COND

End of Track

Controller transferred the last byte of

the last sector without the TC pin becoming active

The last sector is the End of Track sector number

programmed in the Command Phase

Not Used

Always 0

CRC Error

If this bit is set and bit 5 of ST2 is clear

then there was a CRC error in the Address Field of

the correct sector If bit 5 of ST2 is also set then

there was a CRC error in the Data Field

Overrun

Controller was not serviced by the mP

soon enough during a data transfer in the Execution

Phase For read operations indicates a data over-

run For write operations indicates a data underrun

Not Used

Always 0

No Data

Three possible problems

1 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 was found however so it is not a

blank disk

2 Controller cannot read any Address Fields with-

out a CRC error during a Read ID command

3 Controller cannot find starting sector during exe-

cution of Read A Track command

Not Writable

Write Protect pin is active when a

Write or Format command is issued

Missing Address Mark

If bit 0 of ST2 is clear then

the controller cannot detect any Address Field Ad-

dress Mark after two disk revolutions If bit 0 of ST2

is set then the controller cannot detect the Data

Field Address Mark after finding the correct Ad-

dress Field

323 Status Register 2 (ST2)

DESC

SEH

SNS

RESET

000

COND

Not Used

Always 0

Control Mark

Controller tried to read a sector

which contained a deleted data address mark dur-

ing execution of Read Data or Scan commands Or

if a Read Deleted Data command was executed a

regular address mark was detected

CRC Error in Data Field

Controller detected a

CRC error in the Data Field Bit 5 of ST1 is also set

Wrong Track

Only set if desired sector is not

found and the track number recorded on any sector

of the current track is different from the track ad-

dress specified in the Command Phase

Scan Equal Hit

‘‘Equal’’ condition satisfied during

any Scan command

Scan Not Satisfied

Controller cannot find a sector

on the track which meets the desired condition dur-

ing any Scan command

Bad Track

Only set if the desired sector is not

found the track number recorded on any sector on

the track is FFh indicating a hard error in IBM for-

mat and is different from the track address speci-

fied in the Command Phase

PC87306 Datasheet(PDF) 33 Page - National Semiconductor (TI)

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