Table 18 - Description of Command Symbols
NAME DESCRIPTION
SYMBOL
N
Sector Size Code This specifies the number of bytes in a sector. If this parameter is
"00", then the sector size is 128 bytes. The number of bytes
transferred is determined by the DTL parameter. Otherwise the
sector size is (2 raised to the "N'th" power) times 128. All values
up to "07" hex are allowable. "07"h would equal a sector size of
16k. It is the user's responsibility to not select combinations that
are not possible with the drive.
N
SECTOR SIZE
128 bytes
256 bytes
512 bytes
1024 bytes
…
00
01
02
03
..
07
16 kbytes
NCN
ND
New Cylinder
Number
The desired cylinder number.
Non-DMA Mode
Flag
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.
OW
Overwrite
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.
PCN
Present Cylinder The current position of the head at the completion of Sense
Number
Interrupt Status command.
POLL
PRETRK
Polling Disable
When set, the internal polling routine is disabled. When clear,
polling is enabled.
Precompensation Programmable from track 00 to FFH.
Start Track
Number
R
Sector Address
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.
RCN
Relative Cylinder Relative cylinder offset from present cylinder as used by the
Number Relative Seek command.
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