IBM 5-1/4" Diskette Drive Adapter Hardware Reference Manual page 10

Symbol
Name
AO Address Line 0
C Cylinder Number
D Data
D7-DO Data Bus
DTL
Data Length
EDT End of Track
GPL
Gap Length
H
Head Address
HD
Head
HLT
Head Load Time
HUT Head Unload Time
MF FM or MFM Mode
MT
Multi-Track
N Number
Description
AO controls selection of main status
register (AO
=
0) or data register (AO
=
1).
C stands for the current/selected cylinder
(track) number of the medium.
D stands for the data pattern that is going
to be written into a sector.
8-bit data bus, where D7 stands for a
most significant bit, and DO stands for a
least significant bit.
When N is defined as 00, DTL stands for
the data length that users are going to
read from or write to the sector.
EDT stands for the final sector number on
a cylinder.
GPL stands for the length of gap 3
(spacing between sectors excluding VCO
sync field).
H stands for head number 0 or 1, as
specified in ID field.
HD stands for a selected head number 0
or 1. (H
=
HD in all command words).
HL T stands for the head load time in the
FDD (4 to 512 ms in 4·ms increments).
HUT stands for the head unload time after
a read or write operation has occurred (0
to 480 ms in 32-ms increments).
If MF is low, FM mode is selected; if it is
high, MFM mode is selected only if MFM
is implemented.
If MT is high, a multi-track operation is to
be performed. (A cylinder under both HDO
and HD1 will be read or written.)
N stands for the number of data bytes
written in a sector.
Symbol Descriptions (Part 1 of 2)
6 Diskette Adapter