The PC16552D is a dual version of the PC16550D Universal Asynchronous Receiver Transmitter (UART) The two serial channels are completely independent except for a common CPU interface and crystal input On power-up both channels are functionally identical to the 16450 Each channel can operate with on-chip transmitter and receiver FIFOs (FIFO mode) to relieve the CPU of excessive software overhead In FIFO mode each channel is capable of buffering 16 bytes (plus 3 bits of error data per byte in the RCVR FIFO) of data in both the transmitter and receiver All the FIFO control logic is on-chip to minimize system overhead and maximize system efficiency