LPC47M14X datasheet(55/205 Pages) SMSC

55 / 205 page

SMSC DS – LPC47M14X

Page 55

Rev. 05/02/2000

Table 25 – Typical Values for Formatting

FORMAT

SECTOR SIZE

GPL1

GPL2

5.25" Drives

128

512

1024

2048

4096

...

MFM

256

512*

1024

2048

4096

...

3.5" Drives

128

256

512

MFM

256

512**

1024

GPL1 = suggested GPL values in Read and Write commands to avoid splice point between data field and

ID field of contiguous sections.

GPL2 = suggested GPL value in Format A Track command.

*PC/AT values (typical)

**PS/2 values (typical). Applies with 1.0 MB and 2.0 MB drives.

Note:

All values except sector size are in hex.

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 Register 0 to "01" (abnormal

termination), sets 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 nTRK0 pin from the FDD. As long as the nTRK0 pin is low, the DIR pin

remains 0 and step pulses are issued. When the nTRK0 pin goes high, the SE bit in Status Register 0 is set to "1" and

the command is terminated. If the nTRK0 pin is still low after 79 step pulses have been issued, the FDC sets the SE and

the EC bits of Status Register 0 to "1" and terminates the command. 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. At 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.

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