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MVME55006E Single-Board Computer Installation and Use (6806800A37D)
Functional Description Asynchronous Serial Ports
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2.10 Asynchronous Serial Ports
The MVME5500 board uses two TL16C550C universal asynchronous receiver/transmitters
(UARTs) interfaced to the GT-64260B device bus to provide the asynchronous serial interfaces.
EIA232 drivers and receivers reside on board. COM1 signals are wired to an RS-232
transceiver that interfaces to the front-panel RJ-45 connector. COM2 signals are also wired to
a transceiver that interfaces to an on-board 9-pin header (refer to Chapter 5, Connector Pin
Assignments, for more details). An on-board 1.8432 MHz oscillator provides the baud rate clock
for the UARTs.
2.11 Real Time Clock and NVRAM
The SGS-Thomson M48T37V is used by the MVME5500 board to provide 32KB of non-volatile
static RAM, real-time clock and watchdog timer. The watchdog timer, if enabled, can be
programmed to generate either an interrupt or system reset if it expires. Refer to the MK48T37V
Data Sheet for programming information.
The M48T37V consists of two parts:
z A 44-pin 330mil SOIC device that contains the RTC, the oscillator, 32KB of SRAM and
gold-plated sockets for the SNAPHAT battery.
z A SNAPHAT battery that houses the crystal and the battery.
The SNAPHAT battery package is mounted on top of the SOIC MT48T37V device after the
completion of the surface mount process. The battery housing is keyed to prevent reverse
insertion.
Figure 2-2 COM1 Asynchronous Serial Port Connections (RJ-45)
SOUT
RTS#
DTR#
CTS#
DCD#
DSR#
RI#
TL16C550C
4
2
8
7
5
1
TXD
RTS
DTR
RXD
CTS
DCD
GND
SIN
3
NC
NC
RJ45 Connector
6