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ZEUS Technical Manual Detailed hardware description
© 2007 Eurotech Ltd Issue D 53
Serial COM ports
There are seven serial communications ports available on the ZEUS. Three are
provided by the PXA270 and are used for the optional wireless modem, GPS and
IEEE802.15.4 / ZigBee ports.
There are four additional high-speed, 16550 compatible serial UARTs implemented by
an EXAR ST16C554Q Quad UART device. Two of these channels (COM1, COM2) can
be used as standard RS232 serial interfaces, COM3 can be configured as RS232 or
RS485/422, and COM4 can be configured as RS422 or RS485. The table below
provides a summary of the four additional serial ports.
Port Address IRQ
FIFO depth
RX / TX
Signals
COM1 0x10000000 –
0x1000000F
GPIO9 16/16 RS232: Rx, Tx, CTS, RTS, RI,
DSR, DCD, DTR
COM2 0x10800000 –
0x1080000F
GPIO10 16/16 RS232: Rx, Tx, CTS, RTS, RI,
DSR, DCD, DTR
COM3 0x11000000 –
0x1100000F
GPIO12 16/16 RS232: Rx, Tx, CTS, RTS, RI,
DSR, DCD, DTR
or
RS422/485: Rx, Tx
COM4 0x11800010 –
0x1180001F
GPIO11 16/16 RS422/RS485: Rx, Tx
COM1/2 – RS232 interface
Supported on Channel A and B of the external Quad UART, the ports are buffered to
RS232 levels with ±15kV ESD protection, and support full handshaking and modem
control signals. The maximum baud rate is 921.6 Kbaud. COM1 and COM2 ports can
be accessed using DB9 connectors J11 and J15, respectively. For pin assignment and
connector details, see J11 – Serial port – COM1
on page 83 and J15 – Serial port –
COM2
on page 86.
A factory fit option configures COM1 as TTL Level signals to interface to certain
specialized modems. Please contact Eurotech Technical Support
(see page 97) for
details.