Anachip Corp.

www.anachip.com.tw

Rev. 1.0 Dec 16, 2004

4/10

the asynchronous clear sets Q LOW, regardless of the

clock state. If both terms are satisfied simultaneously, the

clear will override the preset.

Output Polarity

Each macrocell can be configured to implement active-high

or active-low logic. Programmable polarity eliminates the

need for external inverters.

Output Enable

The output of each I/O macrocell can be enabled or

disabled under the control of its associated programmable

output enable product term. When the logical conditions

programmed on the output enable term are satisfied, the

output signal is propagated to the I/O pin. Otherwise, the

output buffer is switched into the high-impedance state.

Under the control of the output enable term, the I/O pin can

function as a dedicated input, a dedicated output, or a bi-

directional I/O. Opening every connection on the output

enable term will permanently enable the output buffer and

yield a dedicated output. Conversely, if every connection is

intact, the enable term will always be logically false and the

I/O will function as a dedicated input.

Input/Feedback Select

The PEEL18LV8Z macrocell also provides control over the

feedback path. The input/feedback signal associated with

each I/O macrocell can be obtained from three different

locations; from the I/O input pin, from the Q output of the

flip-flop (registered feedback), or directly from the OR gate

(combinatorial feedback).

Bi-directional I/O

The input/feedback signal is taken from the I/O pin when

using the pin as a dedicated input or as a bi-directional I/O.

(Note that it is possible to create a registered output

function with a bi-directional I/O, refer to Figure 4).

Figure 4 - PEEL18LV8Z I/O Macro cell

Combinatorial Feedback

The signal-select multiplexer gives the macrocell the ability

to feedback the output of the OR gate, bypassing the

output buffer, regardless of whether the output function is

registered or combinatorial. This feature allows the creation

of asynchronous latches, even when the output must be

disabled. (Refer to configurations 5, 6, 7, and 8 in Figure 5.)

Registered Feedback

Feedback also can be taken from the register, regardless

of whether the output function is programmed to be

combinatorial or registered. When implementing a

combinatorial output function, registered feedback allows

for the internal latching of states without giving up the use

of the external output.

Programmable Clock Options

A unique feature of the PEEL18LV8Z is a programmable

clock multiplexer that allows the user to select true or

complement forms of either input pin or product-term clock

sources.

Operates in both 3 Volt and 3.3 Volt Systems

of 2.7 to 3.6 Volts D.C. This allows operation in both 3 Volt

10% (battery operated) and 3.3 Volt 10% (power supply

slower at the lower voltage, but this is typically not an issue

in battery-operated systems (see - A.C. Electrical

CharacteristicsTable 1 - Absolute Maximum Ratings- A.C.

Electrical Characteristics).

Schmitt Trigger Inputs

The PEEL18LV8Z has Schmitt trigger input buffers on all

inputs, including the clock. Schmitt trigger inputs allow

direct input of slow signals such as biomedical and sine

waves or clocks. They are also useful in cleaning up noisy

signals. This makes the PEEL18LV8Z especially desirable

in portable applications where the environment is less

predictable.

Zero Power Feature

The CMOS PEEL18LV8Z features "Zero-Power" standby

operation for ultra-low power consumption. With the "Zero-

Power" feature, transition-detection circuitry monitors the

inputs, I/Os (including CLK) and feedbacks. If these signals

do not change for a period of time greater than

current state and the device automatically powers down.

When the next signal transition is detected, the device will

"wake up" for active operation until the signals stop