SCH3112I-NE SMSC [SMSC Corporation], SCH3112I-NE Datasheet - Page 87

• Manufacturer Part Number: SCH3112I-NE
• Description: LPC IO with 8042 KBC, Reset Generation, HWM and Multiple Serial Ports
• Manufacturer: SMSC [SMSC Corporation]

LPC IO with 8042 KBC, Reset Generation, HWM and Multiple Serial Ports
Datasheet
SMSC SCH311X
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. Issue Read/Write command.
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.
SENSE INTERRUPT STATUS
An interrupt signal is generated by the FDC for one of the following reasons:
1. Upon entering the Result Phase of:
a. Read Data command
b. Read A Track command
c. Read ID command
d. Read Deleted Data command
e. Write Data command
f.
g. Write Deleted Data command
h. Verify command
2. End of Seek, Relative Seek, or Recalibrate command
The Sense Interrupt Status command resets the interrupt signal and, via the IC code and SE bit of
Status Register 0, identifies the cause of the interrupt.
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.
Format A Track command
DATASHEET
71
Rev 0.2 (09-28-04)