PC87311AVF datasheet(29/78 Pages) NSC

29 / 78 page

40 FDC Command Set Description (Continued)

FIFO

Enable FIFO for Execution Phase data transfers De-

fault after a software reset if the LOCK bit is 0 If the LOCK

bit is 1 then the FIFO bit will retain its previous value after a

software reset

0 e

FIFO enabled for both reads and writes

1 e FIFO disabled (default)

POLL

Disable for Drive Polling Mode Default after a soft-

ware reset

0 e Enable polling mode An interrupt is generated after a

reset (default)

1 e

Disable drive polling mode If the Configure command

is issued within 500 ms of a hardware or software reset

then an interrupt will not be generated In addition the

four Sense Interrupt commands to clear the ‘‘Ready

Changed State’’ of the four logical drives will not be

required

THRESH

The FIFO threshold in the Execution Phase of

read and write data transfers Programmable from 00 to 0F

hex Defaults to 00 after a software reset if the LOCK bit is

0 If the LOCK bit is 1 then THRESH will retain its value A

high value of THRESH is suited for slow response systems

and a low value of THRESH is better for fast response sys-

tems

PRETRK

Starting track number for write precompensation

Programmable from track 0 (‘‘00’’) to track 255 (‘‘FF’’) De-

faults to track 0 (‘‘00’’) after a software reset if the LOCK bit

is 0 If the LOCK bit is 1 then PRETRK will retain its value

422 Dumpreg Command

The Dumpreg command is designed to support system run-

time diagnostics and application software development and

debug This command has a one byte command phase and

a ten byte result phase which return the values of parame-

ters set in other commands That is the PTR (Present Track

microcode has stored for each drive The Step Rate Time

Motor Off and Motor On Times and the DMA bit are all set

in the Specify command

The sixth byte of the result phase varies depending on what

commands have been previously executed

If a format command has previously been issued and no

reads or writes have been issued since then this byte will

contain the sectors per track value If a read or write com-

mand has been executed more recently than a format com-

mand this byte will contain the end of track value The

LOCK bit is set in the Lock command The eighth result byte

also contains the bits programmed in the Perpendicular

Mode command The last two bytes of the Dumpreg Result

Phase are set in the Configure command After a hardware

or software reset the parameters in the result bytes will be

set to their appropriate default values

Note

Some of these parameters are unaffected by a software reset de-

pending on the state of the LOCK bit

423 Format Track Command

This command will format one track on the disk in IBM ISO

or Perpendicular Format After the index hole is detected

data patterns are written on the disk including all gaps ad-

dress marks Address Fields and Data Fields The exact

format is determined by the following parameters

1 The MFM bit in the Opcode (first command) byte which

determines the format of the Address Marks and the en-

coding scheme

2 The IAF bit in the Mode command which selects be-

tween IBM and ISO format

3 The WGATE and GAP bits in the Perpendicular Mode

command which select between the conventional and

Toshiba Perpendicular format

4 The Bytes per Sector code which determines the sector

size

5 The Sector per Track parameter which determines how

many sectors will be formatted on the track

6 The Data Pattern byte which is used as the filler byte in

the Data Field of each sector

PC87311AVF Datasheet(PDF) 29 Page - National Semiconductor (TI)

PC87311AVF Datasheet(HTML) 29 Page - National Semiconductor (TI)

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78

Datasheet Download

Link URL