The CD74FCT652 is an octal bus transceiver and resistor with 3-state outputs. It consists of D-type flip-flops and control circuitry, arranged for multiplexed transmission of data directly from the data bus or from the internal storage registers. Output-enable (OEAB and OEBA) inputs control the transceiver functions. The select-control (SAB and SBA) inputs select real-time-data or stored-data transfer. A low-input level selects real-time data, and a high-input level selects stored data. The select-control circuitry eliminates the typical decoding glitch that occurs in a multiplexer during the transition between stored data and real-time data. The device uses a small-geometry BiCMOS technology. The output stage is a combination of bipolar and CMOS transistors that limits the output high level to two diode drops below VCC. This resultant lowering of output swing (0 V to 3.7 V) reduces power-bus ringing [a source of electromagnetic interference (EMI)] and minimizes VCC bounce and ground bounce and their effects during simultaneous output switching. The output configuration also enhances switching speed and is capable of sinking 64 mA. Data on the A or B data bus, or both, can be stored in the internal D-type flip-flop by low-to-high transitions at the appropriate clock terminal (CLKAB and CLKBA), regardless of the state of the select or enable control terminals. When SAB and SBA are in the real-time-transfer mode, it also is possible to store data without using the internal D-type flip-flop by simultaneously enabling OEAB and OEBA. In this configuration, each output reinforces its input. Thus, when all other data sources to the two sets of bus lines are at high impedance, each set of bus lines remains at its last state. To ensure the high-impedance state during power up or power down, OEBA 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 (B to A). OEAB should be tied to GND through a pulldown resistor; the minimum value of the resistor is determined by the current-sourcing capability of the driver (A to B). The CD74FCT652 is characterized for operation from 0C to 70C. |