The ACT533 devices are octal transparent
D-type latches with 3-state outputs. When the
latch-enable (LE) input is high, the Q\ outputs
follow the complements of the data (D) inputs.
When LE is taken low, the Q\ outputs are latched
at the inverted levels set up at the D inputs.
A buffered output-enable (OE)\ input can be used
to place the eight outputs in either a normal logic
state (high or low logic levels) or the
high-impedance state. In the high-impedance
state, the outputs neither load nor drive the bus
lines significantly. The high-impedance state and
increased drive provide the capability to drive bus
lines without need for interface or pullup
(OE)\ does not affect the internal operations of the
latches. Old data can be retained or new data can
be entered while the outputs are in the
To ensure the high-impedance state during power up or power down, (OE)\ should be tied to VCC through a pullup
resistor; the minimum value of the resistor is determined by the current-sinking capability of the driver.