The 'ABT16652 are 16-bit bus transceivers that consist 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. These devices can be used as two 8-bit
transceivers or one 16-bit transceiver.
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 'ABT16652.
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 inputs. 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. 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,
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 SN54ABT16652 is characterized for operation over the full
military temperature range of -55°C to 125°C. The
SN74ABT16652 is characterized for operation from -40°C to