FDC37M81X Datasheet, PDF (62/198 Pages) SMSC Corporation – PC98/99 Compliant Enhanced Super I/O Controller with Keyboard/Mouse Wake-Up

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. Format A Track command
g. Write Deleted Data command
h. Verify command
2. End of Seek, Relative Seek, or Recalibrate
command
3. FDC requires a data transfer during the
execution phase in the non-DMA mode
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.
Table 26 - Interrupt Identification
SE IC
INTERRUPT DUE TO
0
11 Polling
1
00 Normal termination of Seek
or Recalibrate command
Abnormal termination of
1
01 Seek or Recalibrate
command
The Seek, Relative Seek, and Recalibrate
commands have no result phase. The Sense
Interrupt Status command must be issued
immediately after these commands to terminate
them and to provide verification of the head
position (PCN). The H (Head Address) bit in ST0
will always return a "0". If a Sense Interrupt Status
is not issued, the drive will continue to be BUSY
and may affect the operation of the next
command.
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