
IT8673F
7
Table 11-14. Command Set Symbol Descriptions (cont’d)
Symbol
Name
Description
MFM
FM or MFM Mode
If MFM is low, FM Mode (single density) is selected. If MFM is high, MFM Mode
(double density) is selected.
MT
Multi-Track
If MT is high, a Multi-Track operation is to be performed. In this mode, the FDC
will automatically start searching for sector 1 on side 1 after finishing a
READ/WRITE operation on the last sector on side 0.
N
Number
The number of data bytes written into a sector, where:
00 = 128 bytes (PC standard)
01 = 256 bytes
02 = 512 bytes
…
07 = 16 Kbytes
NCN
New Cylinder
Number
A new cylinder number, which is to be reached as a result of the SEEK operation.
Desired position of Head.
ND
Non-DMA Mode
When ND is high, the FDC operates in the Non-DMA Mode.
OW
Overwrite
If OW=1, DC3-0 of the PERPENDICULAR MODE command can be modified.
Otherwise, those bits cannot be changed.
PCN
Present Cylinder
Number
The cylinder number at the completion of a SENSE INTERRUPT STATUS
command. Position of Head at present time.
POLLD
Polling Disable
If POLLD=1, the internal polling routine is disabled.
PRETRK
Precompensation
Starting Track
Number
Programmable from track 0 – 255.
R
Record
The sector number, which will be read or written.
RCN
Relative Cylinder
Number
To determine the relative cylinder offset from present cylinder as used by the
RELATIVE SEEK command.
SC
The number of sectors per cylinder.
SK
Skip
If SK=1, the Read Data operation will skip sectors with a Deleted Data Address
Mark. Or, the Read Deleted Data operation only accesses sectors with a Deleted
Data Address Mark.
SRT
Step Rate Time
The Stepping Rate for the FDD (1 to 16 ms in 1 ms increments). Stepping Rate
applies to all drives (F=1 ms, E=2 ms, etc.).
ST0
ST1
ST2
ST3
Status 0
Status 1
Status 2
Status 3
ST0
3 stand for one of four registers that store the status information after a
command has been executed. This information is available during the Result
phase after command execution. These registers should not be confused with the
Main Status Register (selected by A
0
= 0); ST0
3 may be read only after a
command has been executed and contain information associated with that
particular command.
STP
If STP = 1 during a SCAN operation, the data in contiguous sectors are compared
byte by byte with data sent from the processor (or DMA). If STP = 2, alternate
sectors are read and compared.