These devices consist of bus transceiver circuits, D-type
flip-flops, and control circuitry arranged for multiplexed
transmission of data directly from the data bus or from the internal
Output-enable (OEAB and )
inputs are provided to control the transceiver functions.
Select-control (SAB and SBA) inputs are provided to select whether
real-time or stored data is transferred. The circuitry used for
select control eliminates the typical decoding glitch that occurs in
a multiplexer during the transition between stored and real-time
data. A low input selects real-time data, and a high input selects
stored data. Figure 1 illustrates the four fundamental bus-management
functions that can be performed with the ´BCT652.
Data on the A or B data bus, or both, can be stored in the
internal D-type flip-flops by low-to-high transitions at the
appropriate clock (CLKAB or CLKBA) inputs regardless of the select-
or enable-control pins. When SAB and SBA are in the real-time
transfer mode, it is possible to store data without using the
internal D-type flip-flops by simultaneously enabling OEAB and . In this configuration each output
reinforces its input. Therefore, when all other data sources to the
two sets of bus lines are at high impedance, each set of bus lines
remain at its last state.
The SN54BCT652 is characterized for operation over the full
military temperature range of -55°C to 125°C. The
SN74BCT652 is characterized for operation from 0°C to 70°C.