Emerson MVME55006E manual Asynchronous Serial Ports, Real Time Clock and Nvram

Functional Description Asynchronous Serial Ports

2.10Asynchronous 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.

Figure 2-2 COM1 Asynchronous Serial Port Connections (RJ-45)

TL16C550C

DCD#

SIN

SOUT DTR#

DSR#

RTS#

CTS#

RI#

NC

NC

DCD 1

RXD 5

TXD 4

DTR 8

GND 3 6

RTS 2

CTS 7

RJ45 Connector

2.11Real 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:

zA 44-pin 330mil SOIC device that contains the RTC, the oscillator, 32KB of SRAM and gold-plated sockets for the SNAPHAT battery.

zA 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.

44 MVME55006E Single-Board Computer Installation and Use (6806800A37D)