PC87303 datasheet(48/114 Pages) NSC

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40 FDC Command Set Description (Continued)

TABLE 4-17 Motor Off Time (MFT) Values

Data Rate

Mode 1 (TMR e 0)

Mode 2 (TMR e 1)

Units

Value

Range

Value

Range

1 Mbps

MFT c 8

8 – 128

MFT c 512

512 – 8192

500 kbps

MFT c 16

16 – 256

MFT c 512

512 – 8192

300 kbps

MFT c 803

267 – 427

MFT c 25603

853 – 13653

250 kbps

MFT c 32

32 – 512

MFT c 1024

1024 – 16384

Note

Motor Off Time e 0 is treated as MFT e 16

TABLE 4-18 Motor On Time (MNT) Values

Data Rate

Mode 1 (TMR e 0)

Mode 2 (TMR e 1)

Units

Value

Range

Value

Range

1 Mbps

MNT

1 – 128

MNT c 32

32 – 4096

500 kbps

MNT

1 – 128

MNT c 32

32 – 4096

300 kbps

MNT c 103

33 – 427

MNT c 1603

53 – 6827

250 kbps

MNT c 4

4 – 512

MNT c 64

64 – 8192

Note

Motor On Time e 0 is treated as MNT e 128

The Motor Off and Motor On timers are artifacts of the NEC

PD765 These timers determine both the delay from se-

lecting a drive motor until a read or write operation is start-

ed and the delay of deselecting the drive motor after the

command is completed Since the FDC enables the drive

and motor select line directly through the DOR these timers

only provide some delay from the initiation of a command

until it is actually started

4121 Verify Command

The Verify command reads logical sectors containing a Nor-

mal Data AM from the selected drive without transferring

the data to the host This command is identical to the Read

Data command except that no data is transferred during

the Execution Phase

The Verify command is designed for post-format or post-

write verification Data is read from the disk as the control-

ler checks for valid Address Marks in the Address and Data

Fields The CRC is computed and checked against the pre-

viously stored value on the disk The EOT value should be

set to the final sector to be checked on each side If EOT is

greater than the number of sectors per side the command

will terminate with an error and no useful Address Mark or

CRC data will be given

The TC pin cannot be used to terminate this command

since no data is transferred The verify command can simu-

late a TC by setting the EC bit to a 1 In this case the

command will terminate when SC (Sector Count) sectors

have been read (If SC e 0 then 256 sectors will be veri-

fied) If EC e 0 then the command will terminate when

EOT is equal to the last sector to be checked In this case

the Data Length parameter should be set to FFh Refer to

Table 4-10 for the Result Phase values for a successful

completion of the command Also see Table 4-19 for further

explanation of the result bytes with respect to the MT and

EC bits

Command Phase

MFM

DR1

DR0

Track Number

Drive Head Number

Sector Number

Bytes per Sector

End of Track Sector Number

Intersector Gap Length

Data LengthSector Count

Execution Phase

Data is read from disk but not transferred

to the system

Result Phase

Status Register 0

Status Register 1

Status Register 2

Track Number

Head Number

Sector Number

Bytes per Sector

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