Product Reference
2–11
Serial Ports (J11, J13)Four RS-232C serial ports are included on the Little Board/486e CPU. Serial port 2 provides an
optional RS-485 serial interface. Both serial ports support software selec table st andard baud r ates
up to 115.2K baud, 5-8 data bits, and 1, 1.5, or 2 sto p bit s. The IEEE R S232C spe cifica tion l imits
the serial port to 19.2K baud on cables up to 50 fe et in leng th. Th e serial p orts are ba sed o n a
16550 UART-compatible controller. This is an ad vance d UA RT th at h as a 16-byte FI FO buffe r to
improve throughput.
RS-232C Serial Ports
The Little Board/486e CPU can use 5BC sometimes as an alternate computer. Microprocessor
system provides four standard RS-232C serial po rts a t J11 and J1 3 fo r use w ith:
! Printers
! Modems
! Terminals
! Remote hosts
! Touch input devices
! Any RS-232C serial device
Many devices require handshaking in one or both directions. Consult the documentation for any
device(s) used for information about handshaking, cabling, and other interface considerations.
Information about serial port configuration using SE TUP, is pro vide d in th is ch apter.
RS-485 Serial Port
An RS-485 option is available for Serial Port 2 at J11. Use of the RS-485 option offers a low cost,
easy-to-use communications and networking multidrop interface that is ideally suited to a wide
variety of embedded applications requiring low-to-medium-speed data transfer between two or
more systems.
I/O Addresses
Serial port addresses are fixed and can not be chan ged. Each seri al por t, ho weve r, can be
independently disabled using the SETUP function, freeing its I/O addresses for use by other devices
installed on the PC/104 expansion bus. Po rt add res ses are sho wn in Ta ble 2–7.
Table 2–7. Serial Port I/O Addresses and Interru pts
Port I/O Address Interrupt
Serial 1 3F8h - 3FFh 4
Serial 2 2F8h - 2FFh 3
Serial 3 3E8h – 3EF h 7 or 11
Serial 4 2E8h – 2EF h 5 or 10