PC16550D

Temperature Under Bias. . . . . . . . . . . 0 to +70
Storage Temperature. . . . . . . . . . . -65 to +150
All Input or Output Voltages
with Respect to V_SS. . . . . . . . . . . ..-0.5V to +7.0V
Power Dissipation. . . . . . . . . . . .. . . . . . . . . . .1W
Note: Maximum ratings indicate limits beyond which permanent damage may occur. Continuous operation at these limits is not intended and should be limited to those conditions specified under DC electrical characteristics.

The PC16550D is an improved version of the original 16450 Universal Asynchronous Receiver/Transmitter (UART).

Functionally identical to the 16450 on powerup (CHARACTER mode)* the PC16550D can be put into an alternate mode (FIFO mode) to relieve the CPU of excessive software overhead.

In PC16550D internal FIFOs are activated allowing 16 bytes (plus 3 bits of error data per byte in the RCVR FIFO) to be stored in both receive and transmit modes. All the logic is on chip to minimize system overhead and maximize system efficiency. Two pin functions have been changed to allow signalling of DMA transfers.

The UART performs serial-to-parallel conversion on data characters received from a peripheral device or a MODEM, and parallel-to-serial conversion on data characters of PC16550D received from the CPU. The CPU PC16550D can read the complete status of the UART at any time during the functional operation. Status information reported includes the type and condition of the transfer operations being performed by the UART, as well as any error conditions (parity, overrun, framing, or break interrupt).

The UART PC16550D includes a programmable baud rate generator that is capable of dividing the timing reference clock input by divisors of 1 to (216b1), and producing a 16 c clock for driving the internal transmitter logic. Provisions are also included to use this 16 c clock to drive the receiver logic. The UART PC16550D has complete MODEM-control capability, and a processor- interrupt system. Interrupts can be programmed to the user's requirements, minimizing the computing required to handle the communications link.

The UART PC16550D is fabricated using National Semiconductor's advanced M²CMOS process.