Ref: 11030032
Title: UPS Interface Specification for 3S/400 Servers
date: 8/1/89

Copyright 3Com Corporation, 1991.  All rights reserved.

This specification provides the information needed to attach
uninterruptible power supply (UPS) products to the 3Com 3S/400
server.

3Com's 3S/400 server is a 386-based network server that operates
with an enhanced version of 3Com's tape-delivered 3+ and 3+Open
network software.  Designed exclusively for network usage, the
3S/400 does not require such failure-prone components as floppy
drives, a keyboard, or a monitor.


AC Power-Failure Protection

The 3S/400 server can sense and react to a signal indicating AC
power loss from the UPS, maintaining data integrity at the server
and giving users the opportunity to close applications at the
workstation and save data prior to system shutdown.  This is
accomplished by plugging the 3S/400 server's AC power cord into
the UPS and attaching a special cable from the UPS to the 3S/400
server's asynchronous serial port.

Note:  This feature is not supported in 3+Open for 3S/400 version
1.0 software.

When AC power is lost, the UPS sends a signal on the cable to the
server that initiates the following sequence of events:

1.  The 3S/400 operates normally for up to four minutes (the time
    period is user-selectable).  Most AC power losses (about 80%)
    last two minutes or less.  The server continues to operate
    normally if AC power is restored during this period.

2.  If AC power is not restored within the specified time, the
    server broadcasts the message "AC power failure has been
    detected" in a popup window on all users' workstations.

3.  After the maximum of four minutes, the 3S/400 server begins
    to shut down all 3+ services.  All data from memory is
    written to the server's hard disk to maintain data integrity.

4.  The 3S/400 server turns off and signals the UPS to turn off.
    This saves the UPS battery charge in case the AC power is
    cycled on and off.

5.  When AC power is restored, the 3S/400 server reboots and
    returns to normal operation.


Selecting a UPS

3Com does not manufacture a UPS or the cable needed to connect
the 3S/400 to a UPS.  However, 3Com recommends the Intelligent
Power System (IPS), manufactured by Elgar, one of the largest UPS
dealers in the United States.  (Their toll-free phone number is
1-800-73ELGAR.)  The following Elgar IPS models can be used with
3Com's 3S/400-series servers:  400+600, 560, 560x, 1100, and
1100x.


Load Configurations

When selecting a UPS, consider the power load of different 3S/400
configurations.  The equipment should be able to run from the UPS
for at least eight minutes after AC power loss.  Anything less
than eight minutes should be considered as an overload condition
and a higher rated UPS should be used.

Following are approximate wattage requirements for some typical
equipment configurations.

    3S/400                                250 Watts

    3S/400 and 1 Disk Expansion Unit      500 Watts
    or 1 netstation

    3S/400 and 2 Disk Expansion Units     750 Watts
    or 2 netstations

    3S/400 and 3 Disk Expansion Units    1000 Watts
    or 3 netstations


UPS-to-3S/400 Cable

Because 3Com does not manufacture the cable needed to connect the
3S/400 to the UPS, you should contact the UPS manufacturer to buy
a cable.  For example, the LanSafe cable for connecting the
3S/400 to an Elgar IPS unit is ordered from Elgar.

Note:  3Com does not support home-made cables.

Cables (such as the LanSafe cable) can be produced with a
combination male and female connector that allow continued use of
the 3S/400 asynchronous serial port.  The pins on the connector
for UPS status are not normally used by the serial port device.

The signals required to the 3S/400 asynchronous serial port, DSUB
(DB25) connector are:

    AC power is ok        -9 VDC     Pin 13 (ref to Pin 7)
    AC power failure      +9 VDC     Pin 13 (ref. to Pin 7)
    Inverter shutdown     +9 VDC     Pin 19 (ref. to Pin 7)


3+ Software Setup

Follow these steps to set up the 3S/400 server's 3+ software for
use with a UPS:

1.  Check to see that the server's CONFIG.SYS file contains the
    following line:

                      device=\3drivers\Pfail.sys

    This line loads the driver for the power failure warning
    system.  (Note that this driver was written specifically for
    the Elgar Intelligent Power System.)

    If desired, you can specify at the end of the line the number
    of seconds the server will wait after a power failure occurs
    before it warns the network users to log off. The delay can
    be from 0 to 3540 seconds (59 minutes).  For example, the
    following line specifies a delay of five minutes:

                    device=\3drivers\Pfail.sys 300

    If no value is specified, the default is 180 seconds (three
    minutes).

    For instructions on how to modify a server's CONFIG.SYS file,
    refer to the 3+ Network Tuning Guide.

2.  Add the RECVMSG command to each user's AUTOUSER.BAT file.
    The command allows a user to receive the server's power
    failure warning message.  For complete details on the RECVMSG
    command, refer to the 3+ Administrator Guide included with
    3+ software for the 3S/400.
