PC87334VLJ datasheet(45/102 Pages) NSC

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40 FDC Command Set Description (Continued)

TABLE 4-11 SK Effect on the Read Deleted Data Command

Data Type

Sector Read

CM Bit (ST2)

Description of Results

Normal

No Further Sectors Read

Deleted

Normal Termination

Normal

Sector Skipped

Deleted

Normal Termination

4110 Read Deleted Data Command

The Read Deleted Data command reads logical sectors

containing a Deleted Data AM from the selected drive and

makes the data available to the host mP This command is

identical to the Read Data command except for the setting

of the CM bit in ST2 and the skipping of sectors The effect

of SK on the Read Deleted Data command is summarized in

Table 4-11 See Table 4-10 for the state of the result bytes

for a Normal Termination of the command

Command Phase

MFM

IPS

DR1

DR0

Track Number

Drive Head Number

Sector Number

Bytes per Sector

End of Track Sector Number

Intersector Gap Length

Data Length

Execution Phase

Data read from disk drive is transferred

to system via DMA or Non-DMA modes

Result Phase

Status Register 0

Status Register 1

Status Register 2

Track Number

Head Number

Sector Number

Bytes per Sector

4111 Read ID Command

The Read ID command finds the next available Address

Field and returns the ID bytes (track head sector bytes per

sector) to the mP in the Result Phase There is no data

transfer during the Execution Phase of this command An

interrupt is generated when the Execution Phase is complet-

The controller first simulates the Motor On time for the se-

lected drive internally The user must turn on the drive motor

directly by enabling the appropriate drive and motor select

disk interface outputs with the Digital Output Register

(DOR) The Read ID command does not perform an implied

seek

After waiting the Motor On time the controller starts the

Data Separator and waits for the Data Separator to find the

next sector Address Field If an error condition occurs the

IC bits in ST0 are set to Abnormal Termination and the

controller enters the Result Phase Possible errors are

1 The mP aborted the command by writing to the FIFO If

there is no disk in the drive the controller hangs up The

P must then take the controller out of this hung state by

writing a byte to the FIFO This puts the controller into the

Result Phase

2 Two index pulses were detected since the search began

and no AM has been found If the Address Field AM was

never found the MA bit is set in ST1

Command Phase

MFM

XXXHDDR1

DR0

Execution Phase

Controller reads first ID Field header

bytes it can find and reports these bytes to the system in the

result bytes

Result Phase

Status Register 0

Status Register 1

Status Register 2

Track Number

Head Number

Sector Number

Bytes per Sector

4112 Read A Track Command

The Read A Track command reads sectors in physical order

from the selected drive and makes the data available to the

host This command is similar to the Read Data command

with the following exceptions

1 The controller waits for the index pulse before searching

for a sector Address Field If the mP writes to the FIFO

before the index pulse the command enters the Result

Phase with the IC bits in ST0 set to Abnormal Termina-

tion

2 A comparison of the sector Address Field ID bytes will be

performed except for the sector number The internal

sector address is set to 1 and then incremented for each

successive sector read

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