SYMBOL
MT
N
NCN
ND
OW
PCN
POLL
PRETRK
R
RCN
SC
Table 19 - Description of Command Symbols
NAME
DESCRIPTION
Multi-Track
When set, this flag selects the multi-track operating mode. In this
Selector
mode, the FDC treats a complete cylinder under head 0 and 1 as
a single track. The FDC operates as this expanded track started
at the first sector under head 0 and ended at the last sector under
head 1. With this flag set, a multitrack read or write operation will
automatically continue to the first sector under head 1 when the
FDC finishes operating on the last sector under head 0.
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
00 128 Bytes
01 256 Bytes
02 512 Bytes
03 1024 Bytes
…
…
07 16K Bytes
New Cylinder
The desired cylinder number.
Number
Non-DMA Mode When set to 1, indicates that the FDC is to operate in the non-
Flag
DMA mode. In this mode, the host is interrupted for each data
transfer. When set to 0, the FDC operates in DMA mode.
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.
Present Cylinder The current position of the head at the completion of Sense
Number
Interrupt Status command.
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
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.
Relative Cylinder Relative cylinder offset from present cylinder as used by the
Number
Relative Seek command.
Number of
The number of sectors per track to be initialized by the Format
Sectors Per Track command. The number of sectors per track to be verified during a
Verify command when EC is set.
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