IDT74ALVCHR162269A

This 12-bit to 24-bit registered bus exchanger is used in applications in which two separate ports must be multiplexed onto, or demultiplexed from, a single port.

It is particularly suitable as an interface between synchronous DRAMs and high-speed microprocessors. Data is stored in the internal B-port registers on the low-to-high transition of the clock (CLK) input when the appropriate clock-enable (CLKENA) inputs are low. Proper control of these inputs allows two sequential 12-bit words to be presented as a 24-bit word on the B-port.

For data transfer in the B-to-A direction, a single storage register is provided. The select SEL line selects 1B or 2B data for the A outputs. The register on the A output permits the fastest possible data transfer, thus extending the period during which the data is valid on the bus.

The control terminals are registered so that all transactions are synchronous with CLK. Data flow is controlled by the active-low output enables (OEA, OEB1 and OEB2).

The ALVCHR162269A has series resistors in the device output structure which will significantly reduce line noise when used with light loads. This driver has been designed to drive ±12mA at the designated threshold levels.

The ALVCHR162269A has "bus-hold" which retains the inputs' last state whenever the input goes to a high impedance. This prevents floating inputs and eliminates the need for pull-up/down resistors.