
SMSC DS – FDC37N958FR
Page 72
Rev. 09/01/99
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.
2.
Seek command - Step to the proper track
Sense Interrupt Status command - Terminate
the Seek command
Read ID - Verify head is on proper track
Issue Read/Write command.
3.
4.
The Seek command does not have a result
phase. Therefore, it is highly recommended that
the Sense Interrupt Status command be 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,
recommended that the user service all pending
interrupts through the Sense Interrupt Status
command.
it
is
highly
Sense Interrupt Status
An interrupt signal on the FDC’s IRQ pin 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.
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.
Table 34
- Interrupt Identification
SE
IC
INTERRUPT DUE TO
0
1
00
Normal termination of Seek
or Recalibrate command
Abnormal termination of
Seek or Recalibrate
1
11
01
Polling
command