82077AA Datasheet, PDF(24/62 Page) Intel Corporation – CHMOS SINGLE-CHIP FLOPPY DISK CONTROLLER

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82077AA Datasheet, PDF (24/62 Pages) Intel Corporation – CHMOS SINGLE-CHIP FLOPPY DISK CONTROLLER

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82077AA

Symbol Description

PCN

Present cylinder number The current po-

sition of the head at the completion of

SENSE INTERRUPT STATUS command

POLL

Polling disable When set the internal

polling routine is disabled When clear

polling is enabled

PRETRK Precompensation start track number

Programmable from track 00 to FFH

Sector address The sector number to be

read or written In multi-sector transfers

this parameter specifies the sector num-

ber of the first sector to be read or writ-

ten

RCN

Relative cylinder number Relative cylin-

der offset from present cylinder as used

by the RELATIVE SEEK command

Number of sectors The number of sec-

tors to be initialized by the FORMAT

command The number of sectors to be

verified during a Verify Command when

EC is set

Skip flag When set to 1 sectors contain-

ing a deleted data address mark will auto-

matically be skipped during the execution

of READ DATA If READ DELETED is ex-

ecuted only sectors with a deleted ad-

dress mark will be accessed When set to

ââ0ââ the sector is read or written the

same as the read and write commands

SRT

Step rate interval The time interval be-

tween step pulses issued by the

82077AA Programmable from 0 5 to 8

milliseconds in increments of 0 5 ms at

the 1 Mbit data rate Refer to the SPECI-

FY command for actual delays

ST0

Status register 0â3 Registers within the

ST1

82077AA that store status information af-

ST2

ter a command has been executed This

ST3

status information is available to the host

during the result phase after command

execution

WGATE Write gate alters timing of WE to allow

for pre-erase loads in perpendicular

drives

5 1 Data Transfer Commands

All of the READ DATA WRITE DATA and VERIFY

type commands use the same parameter bytes and

return the same results information The only differ-

ence being the coding of bits 0â4 in the first byte

An implied seek will be executed if the feature was

enabled by the CONFIGURE command This seek is

completely transparent to the user The Drive Busy

bit for the drive will go active in the Main Status Reg-

ister during the seek portion of the command If the

seek portion fails it will be reflected in the results

status normally returned for a READ WRITE DATA

command Status Register 0 (ST0) would contain

the error code and C would contain the cylinder on

which the seek failed

5 1 1 READ DATA

A set of nine (9) bytes is required to place the

82077AA into the Read Data Mode After the READ

DATA command has been issued the 82077AA

loads the head (if it is in the unloaded state) waits

the specified head settling time (defined in the

SPECIFY command) and begins reading ID Address

Marks and ID fields When the sector address read

off the diskette matches with the sector address

specified in the command the 82077AA reads the

sectorâs data field and transfers the data to the

FIFO

After completion of the read operation from the cur-

rent sector the sector address is incremented by

one and the data from the next logical sector is read

and output via the FIFO This continuous read func-

tion is called ââMulti-Sector Read Operationââ Upon

receipt of TC or an implied TC (FIFO overrun un-

derrun) the 82077AA stops sending data but will

continue to read data from the current sector check

the CRC bytes and at the end of the sector termi-

nate the READ DATA Command

N determines the number of bytes per sector (see

Table 5-2 below) If N is set to zero the sector size

is set to 128 The DTL value determines the number

of bytes to be transferred If DTL is less than 128

the 82077AA transfers the specified number of

bytes to the host For reads it continues to read the

entire 128 byte sector and checks for CRC errors

For writes it completes the 128 byte sector by filling

in zeroes If N is not set to 00 Hex DTL should be

set to FF Hex and has no impact on the number of

bytes transferred

Table 5-2 Sector Sizes

Sector Size

128 bytes

256 bytes

512 bytes

1024 bytes

16 Kbytes

The amount of data which can be handled with a

single command to the 82077AA depends upon MT

(multi-track) and N (Number of bytes sector)

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