DESCRIPTION OF PIN FUNCTIONS
BUFFER
QFP/
TQFP
PIN NO.
TYPE
NAME
SYMBOL
DESCRIPTION
19,
Interrupt Request IRQ_A
O24
The interrupt request from the logical device
or IRQIN is output on one of the IRQA-G
signals. Refer to the configuration registers
for more information.
37-40, A, C, D,
E, F,
IRQ_C
IRQ_D
IRQ_E
IRQ_F
If EPP or ECP Mode is enabled, this output is
pulsed low, then released to allow sharing of
interrupts.
OD24
27
57
Chip Select Input nCS
I
When enabled, this active low pin serves as
an input for an external decoder circuit which
is used to qualify address lines above A10.
Reset
RESET
IS
This active high signal resets the chip and
must be valid for 500 ns minimum. The effect
on the internal registers is described in the
appropriate section.
The configuration
registers are not affected by this reset.
FLOPPY DISK INTERFACE
16
10
nRead Disk Data nRDATA
IS
Raw serial bit stream from the disk drive, low
active. Each falling edge represents a flux
transition of the encoded data.
nWrite
Gate
nWGATE
OD48
This active low high current driver allows
current to flow through the write head. It
becomes active just prior to writing to the
diskette.
9
nWrite
Data
nWDATA
nHDSEL
OD48
OD48
This active low high current driver provides the
encoded data to the disk drive. Each falling
edge causes a flux transition on the media.
11
nHead
Select
This high current output selects the floppy disk
side for reading or writing. A logic "1" on this
pin means side 0 will be accessed, while a
logic "0" means side 1 will be accessed.
7
Direction
Control
nDIR
OD48
This high current low active output determines
the direction of the head movement. A logic
"1" on this pin means outward motion, while a
logic "0" means inward motion.
7
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