PC87311AVF datasheet(39/78 Pages) NSC

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40 FDC Command Set Description (Continued)

TABLE 4-14 Motor Off Time (MFT) Values

Data Rate

Mode 1 (TMR e 0)

Mode 2 (TMR e 1)

Units

Value

Range

Value

Range

1 Mbs

MFT c 8

8 – 128

MFT c 512

512 – 8192

500 kbs

MFT c 16

16 – 256

MFT c 512

512 – 8192

300 kbs

MFT c 803

267 – 427

MFT c 25603

853 – 13653

250 kbs

MFT c 32

32 – 512

MFT c 1024

1024 – 16384

Note

Motor Off Time e 0 is treated as MFT e 16

TABLE 4-15 Motor On Time (MNT) Values

Data Rate

Mode 1 (TMR e 0)

Mode 2 (TMR e 1)

Units

Value

Range

Value

Range

1 Mbs

MNT

1 – 128

MNT c 32

32 – 4096

500 kbs

MNT

1 – 128

MNT c 32

32 – 4096

300 kbs

MNT c 103

33 – 427

MNT c 1603

53 – 6827

250 kbs

MNT c 4

4 – 512

MNT c 64

64 – 8192

Note

Motor On Time e 0 is treated as MNT e 128

DMA

This bit selects the data transfer mode in the Execu-

tion Phase of a read write or scan operation

0 e

DMA mode is selected

1 e

Non-DMA mode is selected

4221 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 command can simulate 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 verified) 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 FF hex Refer to Table 4-7 for

the Result Phase values for a successful completion of the

command Also see Table 4-16 for further explanation of

the result bytes with respect to the MT and EC bits

4222 Version Command

The Version command can be used to determine the floppy

controller being used The Result Phase uniquely identifies

the floppy controller version The FDC returns a value of

90 hex in order to be compatible with the 82077 The

DP8473 and other NEC765 compatible controllers will re-

turn a value of 80 hex (invalid command)

4223 Write Data Command

The Write Data command receives data from the host and

writes logical sectors containing a Normal Data AM to the

selected drive The operation of this command is similar to

the Read Data command except that the data is transferred

from the mP to the controller instead of the other way

around

The controller will simulate the Motor On time before start-

ing the operation If implied seeks are enabled the seek and

sense interrupt functions are then performed The controller

then starts the Data Separator and waits for the Data Sepa-

rator to find the next sector Address Field The controller

compares the Address ID (track head sector bytes per

sector) with the desired ID specified in the Command

Phase If there is no match the controller waits to find the

next sector Address Field This process continues until the

desired sector is found If an error condition occurs the IC

bits in ST0 are set to Abnormal Termination and the con-

troller 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 will hang up

The mP must then take the controller out of this hung

state by writing a byte to the FIFO This will put the con-

troller into the Result Phase

2 Two index pulses were detected since the search began

and no valid ID has been found If the track address ID

differs the WT bit or BT bit (if the track address is FF hex)

will be set in ST2 If the head sector or bytes per sector

code did not match the ND bit is set in ST1 If the Ad-

dress Field AM was never found the MA bit is set in ST1

3 The Address Field was found with a CRC error The CE

bit is set in ST1

4 If the controller detects the Write Protect disk interface

input is asserted bit 1 of ST1 is set

If the correct Address Field is found the controller waits for

all (conventional mode) or part (perpendicular mode) of

GAP2 to pass The controller will then write the preamble

field address marks and data bytes to the Data Field The

data bytes are transferred to the controller by the mP

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