SN74LVCH16652A

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SCAS319J – NOVEMBER 1993 – REVISED DECEMBER 2014

9 Detailed Description

9.1 Overview

The SN74LVCH16652A device 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. The device can be used as

two 8-bit transceivers or one 16-bit transceiver.

Complementary output-enable (OEAB and OEBA) inputs control the transceiver functions. Select-control (SAB

and SBA) inputs select whether real-time or stored data is transferred. A low input level selects real-time data,

and a high input level selects stored data. 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. Figure 5 illustrates the

four fundamental bus-management functions that can be performed with SN74LVCH16652A.

Data on the A or B bus, or both, can be stored in the internal D flip-flops by low-to-high transitions at the

appropriate clock (CLKAB or CLKBA) inputs, regardless of the levels on the select-control or output-enable

inputs. 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-flops by simultaneously enabling OEAB and OEBA. 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 level configuration.

up resistor and OEAB should be tied to GND through a pull-down resistor; the minimum value of the resistor is

determined by the current-sinking/current-sourcing capability of the driver.

Inputs can be driven from either 3.3-V or 5-V devices. This feature allows the use of these devices as translators

in a mixed 3.3-V/5-V system environment.

Active bus-hold circuitry is provided to hold unused or floating data inputs at a valid logic level. Use of pull-up or

pull-down resistors with the bus-hold circuitry is not recommended. The bus-hold circuitry is part of the input

circuit and is not disabled by OE or DIR.

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