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2.4.3 Sector Select Switch Assembly
The sector select switch assembly (see Figure 2-9) sets the number of sectors per track.
Any number of sectors up to 128 can be selected.
1 2
3
4
5
6
7 8
1 ON
~ ~ ~ ~ ~ ~ ~ ~
0 OFF
SECTOR COUNT
DISPOSITION SWITCH
Figure 2-9 Sector Select Switch
Segment 1 of this assembly determines the disposition of odd or remainder bytes. These
are extra bytes that must be allocated when the available bytes per track are not evenly
divisible by the number of sectors per track. With segment 1 in the 0 position, odd bytes
are grouped together in an extra sector at the end of the track. With this segment in the 1
position, the last sector is reduced to account for odd bytes.
INDEX
Jl
n
If
PULSE
I
I
I
"SA"
"SA"
"SA"
"SA"
I
"SA"
I
SECTOR
0
n
1
~S
31
n
32
n(33)
I
0
rL
PULSE
F "0"
(620
(620)
(620)
(620)
f-20~
(620)
BYTES
BYTE
I
(EXTRA SECTOR)
I
"SA"
"SA"
"SA"
"SA"
I
"SA"
I
SECTOR
0
n
~$
31
n
32
I
0
rL
PULSE
(621)
(621 )
(621 )
608 BYTE
I
(621 )
F"1"
I
(LAST SECTOR)
Figure 2-10 Sector Allocation
Figure 2-10 illustrates the allocation of 33 sectors with segment 1 of the sector select
switch assembly in both the 0 and 1 positions.
2-7
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