GM82C803CN Datasheet, PDF (54/84 Pages) List of Unclassifed Manufacturers – 2.88 MB FDC/ Dual UARTs with FIFO/PIO(EPP/ ECP)/ IDE Interface/ S-IR/ PnP

GM82C803CN
Table 4-27 . Status Register 0 Termination Codes
Seek End
Bit5
0
1
1
Interrupt Code
Bit6
Bit7
1
1
0
0
1
0
Cause
Ready line changed state
Normal Seek or Recalibrate Termination
Abnormal Seek or Recalibrate Termination
The Sense Interrupt Status command is used in conjunction with the Seek or Recalibrate commands which have no
result phase . When the disk drive has reached the desired head position , the FDC will set the Interrupt line true .
The Host must then issue a Sense Interrupt Status command to determine the actual cause of the interrupt , which
could be Seek End of a change in ready status from one of the drives .
Specify
The Specify command sets the initial values for each of the three internal timers. the HUT(Head Unload Time) defines
the time from the end of the execution phase of one of the read/write commands to the head unload state . This timer is
programmable from 16 to 240ms in increments of 16ms ( 01 = 16ms , 02 = 32ms , ... ,0F = 240ms) . The SRT ( Step
Rale Time ) defines the time interval between adjacent slop pulses . This timer is programmable from 1 to 16ms in incr-
ements of 1ms ( F = 1ms , E = 2ms , D = 3ms ... 0 = 16ms ) . The HLT(Head Load Time ) defines the time between
when the Head Load signal goes high and the read/write operation starts. This timer is programmable from 2 to 254ms
in increments of 2ms ( 01 = 2ms , 02 = 4ms , 03 = 6ms ... 7F = 254ms ) . The timeintervals mentioned above are affect-
ed by the data rate . The values are for 500Kbps MFM ( 250Kbps FM ) . For a 300Kbps MFM data rate( 150Kbps FM)
, these values should be multiplied by 1.6667 and or 250 Kbps MFM ( 125Kbps FM) , these values should be doubled .
For 1Mbps MFM , the values should be divides by 2. The choice of DMA or non-DMA operation is made by the ND
(Non-DMA ) bit. When this bit is high (ND = 1) the Non-DMA mode id deleted and when ND=0 , the DMA mode is
selected.
Sense Drive Status
This command may be used by the Host whenever it wished to obtain the status of the FDDs . Status Register 3 conta-
ins the drive status information stored internally in FDC register.
Verify
This command is used to verify the data stored on disk , and acts exactly like a Read Data command except that no
data is transferred to the host . Data is read from the disk . CRC compiled and checked against the previously stored
value.
Because no data is transferred to the Host . TC cannot be used to terminate this command . By setting the EC bit to 1 ,
an implicit TC will be issued to the FDC. This implicit TC will occur when the SC value has decrement to 0 ( an SC
value of 0 will verify 256 sectors) . This command can also be terminated by setting the EC bit to 0 and the EOT value
equal to the final sector to be checked . If EC is set to 0 DLT/SC should be programmed to FFH . Refer to Table 4-22
and 4-28 for information concerning the values of MT and EC versus SC and EOT value.