FDC37M607 datasheet(59/182 Pages) SMSC

59 / 182 page

CONTROL COMMANDS

Control

commands

differ

from

the

other

commands in that no data transfer takes place.

Three commands generate an interrupt when

complete: Read ID, Recalibrate, and Seek. The

other control commands do not generate an

interrupt.

Read ID

The Read ID command is used to find the

present position of the recording heads.

The

FDC stores the values from the first ID field it is

able to read into its registers. If the FDC does

not find an ID address mark on the diskette after

the second occurrence of a pulse on the

nINDEX pin, it then sets the IC code in Status

the MA bit in Status Register 1 to "1", and

terminates the command.

The following commands will generate an

interrupt upon completion. They do not return

any result bytes. It is highly recommended that

control commands be followed by the Sense

Interrupt Status command. Otherwise, valuable

interrupt status information will be lost.

Recalibrate

This command causes the read/write head

within the FDC to retract to the track 0 position.

The FDC clears the contents of the PCN

counter and checks the status of the nTR0 pin

from the FDD. As long as the nTR0 pin is low,

the DIR pin remains 0 and step pulses are

issued. When the nTR0 pin goes high, the SE

bit in Status Register 0 is set to "1" and the

command is terminated. If the nTR0 pin is still

low after 79 step pulses have been issued, the

FDC sets the SE and the EC bits of Status

Disks capable of handling more than 80 tracks

per side may require more than one Recalibrate

command to return the head back to physical

Track 0.

The Recalibrate command does not have a

result phase.

The Sense Interrupt Status

command must be issued after the Recalibrate

command to effectively terminate it and to

provide verification of the head position (PCN).

During the command phase of the recalibrate

operation, the FDC is in the BUSY state, but

during the execution phase it is in a NON-BUSY

state.

this

time,

another

Recalibrate

command may be issued, and in this manner

parallel Recalibrate operations may be done on

up to four drives at once.

Upon power up, the software must issue a

Recalibrate command to properly initialize all

drives and the controller.

Seek

The read/write head within the drive is moved

from track to track under the control of the Seek

command. The FDC compares the PCN, which

is the current head position, with the NCN and

performs the following operation if there is a

difference:

PCN < NCN: Direction signal to drive set to

"1" (step in) and issues step pulses.

PCN > NCN: Direction signal to drive set to

"0" (step out) and issues step pulses.

The rate at which step pulses are issued is

controlled by SRT (Stepping Rate Time) in the

Specify command.

After each step pulse is

issued, NCN is compared against PCN, and

when NCN = PCN the SE bit in Status Register

0 is set to "1" and the command is terminated.

During the command phase of the seek or

recalibrate operation, the FDC is in the BUSY

state, but during the execution phase it is in the

NON-BUSY state. At this time, another Seek or

Recalibrate command may be issued, and in

FDC37M607 Datasheet(PDF) 59 Page - SMSC Corporation

FDC37M607 Datasheet(HTML) 59 Page - SMSC Corporation

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 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 ...More

Datasheet Download

Link URL