DESCRIPTION OF PIN FUNCTIONS
Interrupt Request IRQ_A
A, C, D,
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.
If EPP or ECP Mode is enabled, this output is
pulsed low, then released to allow sharing of
27 Chip Select Input nCS
When enabled, this active low pin serves as
an input for an external decoder circuit which
is used to qualify address lines above A10.
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 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.
This active low high current driver allows
current to flow through the write head. It
becomes active just prior to writing to the
This active low high current driver provides the
encoded data to the disk drive. Each falling
edge causes a flux transition on the media.
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.
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.