Table 18 - Description of Command Symbols
The desired cylinder number.
When set to 1, indicates that the FDC is to operate in the non-DMA
mode. In this mode, the host is interrupted for each data transfer.
When set to 0, the FDC operates in DMA mode, interfacing to a DMA
controller by means of the DRQ and nDACK signals.
The bits D0-D3 of the Perpendicular Mode Command can only be
modified if OW is set to 1. OW id defined in the Lock command.
Present Cylinder The current position of the head at the completion of Sense Interrupt
When set, the internal polling routine is disabled. When clear, polling
Precompensation Programmable from track 00 to FFH.
The sector number to be read or written. In multi-sector transfers,
this parameter specifies the sector number of the first sector to be
read or written.
Relative Cylinder Relative cylinder offset from present cylinder as used by the Relative
Number of Sectors The number of sectors per track to be initialized by the Format
command. The number of sectors per track to be verified during a
Verify command when EC is set.
When set to 1, sectors containing a deleted data address mark will
automatically be skipped during the execution of Read Data. If Read
Deleted is executed, only sectors with a deleted address mark will be
accessed. When set to "0", the sector is read or written the same as
the read and write commands.
Step Rate Interval
The time interval between step pulses issued by the FDC.
Programmable from 0.5 to 8 milliseconds in increments of 0.5 ms at
the 1 Mbit data rate. Refer to the SPECIFY command for actual
Registers within the FDC which store status information after a
command has been executed. This status information is available to
the host during the result phase after command execution.
Alters timing of WE to allow for pre-erase loads in perpendicular