Liebert 232 user manual Network Communications, Hardware Accessories Keypad display

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

	EIA -232
Workstation	(Up to 38.4 kbps)
	Workstation

Modem

	EIA -232
Dial up	(Up to 38.4 kbps
	SiteGate-232
telephone line
	Modem

UCM 10-8

DCU

RCM 10U

RCMEXP

IGM DC 1

CMnet	OCM-8
EIA -485
38.4 kbps

50nodes maximum

Figure 2: System Architecture (Small System)

Rev. (08-JULY-98) 4 © 1996-98 Liebert Corporation