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Controller PCB
Table 3-8 FDC Symbols (cont'd)
SYMBOL
NAME
DESCRIPTION
GPL
Gap Length
Specifies length of Gap 3 (spacing
between sectors excluding VCO Sync.
Field).
H
Head Address
Specifies the head number 0 or 1, as
specified in the ID field.
HD
Head
Specifies the selected head number 0 or
1. (H
=
HD in all command words.)
HLT
Head Load Time
Indicates the head load time in the FDD
(2 to 256 ms in 2-ms increments).
HUT
Head Unload Time
Indicates the head unload time after a
read or write operation has occurred (0
to 240 ms in 16-ms increments).
MF
FM or MFM Mode
If MF is Low, FM Mode is selected; if
High, MFM Mode is selected only if
MFM is implemented.
MT
Multi-Track
If MT is High, a multitrack operation is
to be performed. (A cylinder under both
HDO and HDI is read or written.)
N
Number
Specifies the number of data bytes writ-
ten in a sector.
NCN
New Cylinder
New cylinder number, which is going to
Number
be reached as a result of the Seek opera-
tion. Desired position of head.
ND
Non-DMA Mode
Signals that operation is Non-DMA
Mode.
PCN
Present Cylinder
Designates cylinder number at the
Number
completion of Sense Interrupt Status
Command, indicating the position of the
head at present time.
3-25
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