IMP16C550A

The IMP16C550A UART (universal asynchronous receiver/transmitter) provides data communications capabilities for microprocessor-based systems including polled and interrupt driven environments. IMP16C550A converts data characters for transfer between a parallel CPU and a serial peripheral device (MODEM). The IMP16C550A provides this traditional 16450 UART functionality with two significant enhancements; it is updated to support complete compatibility with current state-of-the-art CPUs including the 80386, and it is improved to minimize software overhead requirements.

Features of the IMP16C550A are:(1)register set identical to the 16450 set upon power up or resef;(2)16-byte FIFO transmitter and receiver buffers;(3)holding and shift registers handle CPU to serial data synchronization (in IMP16C550A mode);(4)extensive MODEM control function set (CTS, RTS, DSR,DTR, RI and DCD);(5)independent controls for transmit, receive, line status and data set interrupts;(6)TRI-STATE TTL drive for data and control buses;(7)asynchronous communication bits (start, stop and parity) programmable in serial data.Built-in status reporting capabilities provide the CPU with a current status reading of the UART at any time during its operation. Accessible status information includes the type of transfer function in progress,operating conditions and error conditions (parity, overrun, framing or  interrupt). A processor-interrupt system allows for programmable interrupts, thus maximizing computing efficiency in the communications link.Plus, the MODEM control capability provides a complete range of control functions to address the serial devices.

The absolute maximum ratings of the IMP16C550A can be summarized as:(1)temperature under bias:0 to +70°C;(2)storage temperature:-65 to +150°C;(3)all input or output voltages with respect to vss:-0.5V to +7.0V;(4)power dissipation:1W.The transmitter converts parallel data from the CPU into a serial bit stream. During this process, start, stop and optional parity bits are added to the data character as dictated by the asynchronous protocol. These same bits are verified by the receiver when it accepts serial data,before converting and reassembling the character for transmission to the CPU.Additionally, External Clock Input and Output pins allow a crystal oscillator or signal clock to be connected to the Control Logic block of the UART as the main timing reference.