SN54ABT646A, SN74ABT646A

OCTAL BUS TRANSCEIVERS AND REGISTERS

WITH 3STATE OUTPUTS

SCBS069H − JULY 1991 − REVISED MAY 2004

2

POST OFFICE BOX 655303

description/ordering information(continued)

Output-enable (OE) and direction-control (DIR) inputs are provided to control the transceiver functions. In the

transceiver mode, data present at the high-impedance port can be stored in either register or in both.

The select-control (SAB and SBA) inputs can multiplex stored and real-time (transparent mode) data. The

direction control (DIR) determines which bus receives data when OE is low. In the isolation mode (OE high),

A data can be stored in one register and/or B data can be stored in the other register.

When an output function is disabled, the input function still is enabled and can be used to store and transmit

data. Only one of the two buses, A or B, can be driven at a time.

outputs, preventing damaging current backflow through the devices when they are powered down.

resistor; the minimum value of the resistor is determined by the current-sinking capability of the driver.