SN74AS877

The 'AS877 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 SN74AS877 device is capable of performing eight selectable transceiver or port functions, depending on the state of the three select lines S0, S1, and S2. These functions include: transferring data from port A to port B or vice versa (i.e., the transceiver function), transferring data from the register to either port, serial shifting data to either port, performing off-line shifts (with A and B ports in high-impedance state), and clearing the register. Synchronous parallel loading of the internal register can be accomplished from either port on the positive transition of the clock while serially shifting data in via the SERIN input. The 'AS877 is ideally suited for applications needing signature-analysis circuitry to enhance system verification and/or fault analysis. All serial data is shifted right. All SN74AS877 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 SN54AS877 is characterized for operation over the full military temperature range of 55°C to 125°C. The SN74AS877 is characterized for operation from 0°C to 70°C.