SN54AS856

The SN54AS856 features two 8-bit I/O ports (A1-A8 and B1-B8), an 8-bit parallel-load, serial-in, parallel-out shift register, and control logic. With these features, this device is capable of performing eight selectable transceiver or port functions, depending on the state of the three control lines OEA, OEB, and MODE. These functions of SN54AS856 include: transferring data from port A to port B or vice versa (i.e., the transceiver function), serial shifting data to either or both ports, and performing off-line shifts (with A and B ports active as transceivers in a high-impedance state).

Synchronous parallel loading of the internal register SN54AS856 can be accomplished from either port on the positive transition of the clock while serially shifting data in via the SERIN input. The SN54AS856 is ideally suited for applications needing signature-analysis circuitry to enhance system verification and/or fault analysis. All serial data is shifted right. All outputs are buffer-type outputs designed specifically to drive bus lines directly and all are 3-state except for Q8, which is a totem-pole output.

The SN54AS856 is characterized for operation over the full military temperature range of 55°C to 125°C. The SN74AS856 is characterized for operation from 0°C to 70°C.