PC97338 datasheet(109/221 Pages) NSC

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Result Phase

See Table 52 for the state of the result bytes when the

command terminates normally.

3.6.12 The READ ID Command

The READ ID command finds the next available ad-

dress field and returns the ID bytes (track number,

head number, sector number, bytes-per-sector code)

to the microprocessor in the result phase.

The controller reads the first ID Field header bytes it

can find and reports these bytes to the system in the

result bytes.

Command Phase

After the last command phase byte is written, the con-

troller waits the Delay Before Processing time (see

Table 59 on page 117) for the selected drive. During

this time, the drive motor must be turned on by en-

abling the appropriate drive and motor select disk in-

terface output signals via the bits of the Digital Output

Offset 010” on page 77.

First Command Phase Byte, Opcode

See “Bit 6 - Modified Frequency Modulation

(MFM)” on page 96.

Second Command Phase Byte

See “Second Command Phase Byte” on page 96

for a description of the Drive Select (DS1,0) and

Head Select (HD) bits.

Execution Phase

There is no data transfer during the execution phase

of this command. An interrupt is generated when the

execution phase is completed.

The READ ID command does not perform an implied

seek.

After waiting the Delay Before Processing time, the

controller starts the data separator and waits for the

data separator to find the address field of the next

sector. If an error condition occurs, the Interrupt Code

(IC) bits in ST0 are set to abnormal termination (01),

and the controller enters the result phase.

Possible errors are:

• The microprocessor aborted the command by writ-

ing to the FIFO.

If there is no disk in the drive, the controller gets

stuck. The microprocessor must then write a byte

to the FIFO to advance the controller to the result

phase.

• Two pulses of the INDEX signal were detected

since the search began, and no Address Mark

(AM) was found.

When the Address Mark (AM) is not found, the

Missing Address Mark bit (bit 0) is set in ST1. Sec-

tion 3.5.2 on page 89 describes the bits of ST1.

Result Phase

3.6.13 The READ A TRACK Command

The READ A TRACK command reads sectors from

the selected drive, in physical order, and makes the

data available to the host.

7654

3210

Result Phase Status Register 0 (ST0)

Result Phase Status Register 1 (ST1)

Result Phase Status Register 2 (ST2)

Track Number

Head Number

Sector Number

Bytes-Per-Sector Code

7654

3210

MFM

1010

XXX

DS1

DS0

7654

3210

Result Phase Status Register 0 (ST0)

Result Phase Status Register 1 (ST1)

Result Phase Status Register 2 (ST2)

Track Number

Head Number

Sector Number

Bytes-Per-Sector Code

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