5
0776L–PLD–11/08
ATF750C(L)
9. Bus-friendly Pin-keeper Input and I/Os
All input and I/O pins on the ATF750C(L) have programmable “pin-keeper” circuits. If activated,
when any pin is driven high or low and then subsequently left floating, it will stay at that previous
high or low level.
This circuitry prevents unused input and I/O lines from floating to intermediate voltage levels,
which causes unnecessary power consumption and system noise. The keeper circuits eliminate
the need for external pull-up resistors and eliminate their DC power consumption.
Enabling or disabling of the pin-keeper circuits is controlled by the device type chosen in the
logic compiler device selection menu. Please refer to the software compiler table for more
details. Once the pin-keeper circuits are disabled, normal termination procedures are required
for unused inputs and I/Os.
10. Input Diagram
11. I/O Diagram
100K
V
CC
ESD
PROTECTION
CIRCUIT
INPUT
PROGRAMMABLE
OPTION
100K
V
CC
V
CC
DATA
OE
I/O
PROGRAMMABLE
OPTION
