ATF1504BE データシートの表示（PDF） - Atmel Corporation

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ATF1504BE

High-performance CPLD

Atmel Corporation 

2. Input and I/O Pins

2.1 Programmable Pin-keeper Option for Inputs and I/Os

The ATF1504BE offers the option of individually programming each of its input or I/O pin so that

pin-keeper circuit can be utilized. 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 undriven input and

I/O lines from floating to intermediate voltage levels, which causes unnecessary power con-

sumption and system noise. The keeper circuits eliminate the need for external pull-up resistors

and eliminate their DC power consumption.

Figure 2-1 shows the pin-keeper circuit for an Input Pin and Figure 2-2 shows the same for an

I/O pin. The pin-keeper circuit is a weak feedback latch and has an effective resistance that is

approximately 50 kΩ.

Figure 2-1. Input with Programmable Pin-keeper

VCCINT

50K

Figure 2-2. I/O with Programmable Pin-keeper

VCCIO

VCCINT

50K

8 ATF1504BE

3637B–PLD–1/08

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