Liebert 232 - Manual (Page 4)

Rev. (08-JULY-98) © 1996-98 Liebert Corporation
4
Battery: Seven-year lithium battery provides a minimum of 10,000 hours of data retention during
power outages.
Fault Detection: Hardware watchdog timer.
Software Requirements: One LGM module driver as FB #15. Workstation software must be
SiteScan for Windows v2.5b or later, Alert 1.1a or later, and FB Link v2.7 or later.
Protection: ESD protection on Console Port 1. Voltage, current, and ESD protection on Incoming
Power, CMnet, and Console Port 2.
Hardware Accessories: Keypad display.
Listed By: PAZX (UL916), cUL C22.2 No. 205-M1983.
Network Communications
The CMnet is a peer-to-peer network which allows the various control modules to communicate with
each other. An IBM-compatible computer can communicate on the CMnet through the SiteGate-232
when direct-connected (DC) or modem-connected (MC), or it can communicate on the CMnet through
any other module with a Direct-Network (DN) connection. The SiteGate-232 does not have a Direct-
Network (DN) connection.
The CMnet communicates using the EIA-485 standard. A "token passing" scheme is used so that each
module has the token in turn. When a module has the token, it broadcasts whatever information is
appropriate from its FBs, while all other modules on the CMnet listen. Any module may receive
information from any other module, but it may broadcast only when it has the token.
When a module is finished with the token, it passes it to the next module (or back to the gateway, if
using grabless token passing) by broadcasting a token-pass message using the next module's address.
The receiving module must acknowledge this message to complete the pass. The SiteGate-232 listens
for an address which is equal to the total number of modules on the CMnet plus one (also referred to as
the Maxnet value). When the last module on the CMnet attempts to pass the token by broadcasting
the Maxnet value, the SiteGate-232 acknowledges the token and starts the cycle over.
Signal integrity on the CMnet is affected by the wire gauge and the total amount of wire in the
Figure 2: System Architecture (Small System)
Workstation
EIA -232
(Up to 38.4 kbps)
Modem
Dial up
telephone line
Modem
SiteGate-232
UCM 10-8
DCU
RCM 10U
RCMEX P
IGM
DC 1
OCM-8
CMnet
EIA -485
38.4 kbps
50 nodes
max imum
Workstation
EIA -232
(Up to 38.4 kbps