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Chapter 3
Floppy Drive Interface (J14)
The VT82C686B chip provides the floppy controller and supports two floppy drives. The floppy signals
are provided through the 26-pin connector (J14).
The floppy controller will support the 360k, 720k, 1.2M, 1.44M, or 2.88M drives
Table 3-12. Floppy Drive Interface Pin/Signal Descriptions (J14)
Pin # Signal
1
KEY
2
DRVEN0 Drive (Floppy) Density Select 0
3
GND
4
INDEX
5
GND
6
MTR0
7
GND
8
DS1
9
GND
10
DS0
11
MTR1
12
DIR
13
GND
14
STEP
15
WDATA
16
WGATE
17
GND
18
TRK0
19
GND
20
WRTPRT Write Protect – Senses the diskette is write protected.
21
GND
22
RDATA
23
GND
24
HDSEL
25
GND
26
DSKCHG Disk Change – Senses the drive door is open or the diskette has been changed
Notes: The shaded area denotes power or ground. The signals marked with * = Negative true logic.
38
Description
Digital Ground
Index – Sense to detect that the head is positioned over the beginning of a track
Digital Ground
Motor Control 0 – Select motor on drive 0.
Digital Ground
Drive Select 1 – Select drive 1.
Digital Ground
Drive Select 0 – Select drive 0.
Motor Control 1 – Select motor on drive 1.
Direction – Direction of head movement (0 = inward motion, 1 = outward
motion).
Digital Ground
Step – Low pulse for each track-to-track movement of the head.
Write Data – Encoded data to the drive for write operations.
Write Gate – Signal to the drive to enable current flow in the write head.
Digital Ground
Track 0 – Sense detects the head is positioned over track 0.
Digital Ground
Digital Ground
Read Data – Raw serial bit stream from the drive for read operations.
Digital Ground
Head Select – Selects the side for Read/Write operations (0 = side 1, 1 = side 0)
Digital Ground
since the last drive selection.
Reference Manual
Hardware
LittleBoard 700
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