Rainbow Electronics ATF1504ASL - Manual (Page 8)

8
ATF1504AS(L)
0950N–PLD–07/02
Programmable Pin-
keeper Option for
Inputs and I/Os
The ATF1504AS offers the option of programming all input and I/O pins so that pin-
keeper circuits can be utilized. When any pin is driven high or low and then subse-
quently 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.
Input Diagram
Speed/Power
Management
The ATF1504AS has several built-in speed and power management features. The
ATF1504AS contains circuitry that automatically puts the device into a low-power
standby mode when no logic transitions are occurring. This not only reduces power con-
sumption during inactive periods, but also provides proportional power savings for most
applications running at system speeds below 5 MHz. This feature may be selected as a
device option.
I/O Diagram
To further reduce power, each ATF1504AS macrocell has a Reduced Power bit feature.
This feature allows individual macrocells to be configured for maximum power savings.
This feature may be selected as a design option.
All ATF1504AS also have an optional power-down mode. In this mode, current drops to
below 10 mA. When the power-down option is selected, either PD1 or PD2 pins (or
both) can be used to power-down the part. The power-down option is selected in the
design source file. When enabled, the device goes into power-down when either PD1 or
PD2 is high. In the power-down mode, all internal logic signals are latched and held, as
are any enabled outputs.