PC8477B datasheet(29/54 Pages) NSC

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40 Command Set Description (Continued)

TABLE 4-16 Verify Command Result Phase Table

SCEOT Value

Termination Result

DTL used (should be FF hex)

No Errors

EOT s

Sectors per Side

DTL used (should be FF hex)

Abnormal Termination

EOT l

Sectors per Side

SC s

Sectors per Side

No Errors

AND

SC s EOT

SC l

Sectors Remaining

Abnormal Termination

SC l EOT

DTL used (should be FF hex)

No Errors

EOT s

Sectors per Side

DTL used (should be FF hex)

Abnormal Termination

EOT l

Sectors per Side

SC s

Sectors per Side

No Errors

AND

SC s EOT

SC s (EOT x 2)

No Errors

AND

EOT s

Sectors per Side

SC l (EOT x 2)

Abnormal Termination

Note 1

Sectors per Side e number of formatted sectors per each side of the disk

Note 2

Sectors Remaining e number of formatted sectors left which can be read which includes side 1 of the disk if the MT bit is set to 1

Note 3

If MT e 1 and the SC value is greater than the number of remaining formatted sectors on side 0 verifying will continue on side 1 of the disk

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 PC8477B 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

Having finished writing the sector the controller will contin-

ue reading the next logical sector unless one or more of the

following termination conditions occurred

1 The DMA controller asserted TC The IC bits in ST0 are

set to Normal Termination

2 The last sector address (of side 1 if MT was set) was

equal to EOT The EOT bit in ST1 is set The IC bits in

ST0 are set to Abnormal Termination This is the expect-

ed condition during Non-DMA transfers

3 Underrun error The OR bit in ST1 is set The IC bits in

ST0 are set to Abnormal Termination If the mP cannot

service a transfer request in time the last correctly writ-

ten byte will be written to the disk

PC8477B Datasheet(PDF) 29 Page - National Semiconductor (TI)

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