The DNA-SL-501 is a 4-port serial communications board (layer) for PowerDNA distributed automation and control system. This board (layer) offers isolated serial interfaces software-configurable as RS-232 or RS-485. DNA-SL-501 supports up to 1 Mbit/s transfer speed in RS-485 mode or up to 256Kbit/s in RS-232 mode. DNA-SL-501 uses 16550 UART controller on each port (FIFO mode only) and supports half- and full-duplex mode for RS-485.