LPC47M192-NW Standard Microsystems (SMSC), LPC47M192-NW Datasheet - Page 59

• Manufacturer Part Number: LPC47M192-NW
• Manufacturer: Standard Microsystems (SMSC)

Specifications of LPC47M192-NW

• Lead Free Status / RoHS Status: Compliant

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 255 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 256 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.
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:
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 this manner, parallel seek operations may be done on up to four drives
at once.
Note that if implied seek is not enabled, the read and write commands should be preceded by:
1) Seek command - Step to the proper track
2) Sense Interrupt Status command - Terminate the Seek command
3) Read ID - Verify head is on proper track
4)
The Seek command does not have a result phase. Therefore, it is highly recommended that the Sense Interrupt
Status command is issued after the Seek command to terminate it and to provide verification of the head position
(PCN). The H bit (Head Address) in ST0 will always return to a “0”. When exiting POWERDOWN mode, the FDC
clears the PCN value and the status information to zero. Prior to issuing the POWERDOWN command, it is highly
recommended that the user service all pending interrupts through the Sense Interrupt Status command.
SMSC DS – LPC47M192
Issue Read/Write command.
PCN < NCN:
PCN > NCN:
Direction signal to drive set to “1” (step in) and issues step pulses.
Direction signal to drive set to “0” (step out) and issues step pulses.
DATASHEET
Page 59
Rev. 03/30/05