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Table 16 - Description of Command Symbols
SYMBOL
N
NAME
DESCRIPTION
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
The desired cylinder number.
NCN
New Cylinder
Number
Non-DMA Mode
Flag
ND
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.
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.
The current position of the head at the completion of Sense Interrupt
Status command.
When set, the internal polling routine is disabled. When clear, polling
is enabled.
Programmable from track 00 to FFH.
OW
Overwrite
PCN
Present Cylinder
Number
Polling Disable
POLL
PRETRK
Precompensation
Start Track
Number
Sector Address
R
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 offset from present cylinder as used by the Relative
Seek command.
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
delays.
RCN
Relative Cylinder
Number
Number of
Sectors Per Track
SC
SK
Skip Flag
SRT