SMSC TMC2005-JT CASCADING CONNECTION, FIGURE 12 - CASCADE CONNECTION OF 4 HUBS

ARCNET 5 Port HUB Controller

Datasheet

CASCADING CONNECTION

HUBs can be connected in cascade by using the ports as Fig. 12. In the case of cascade connection, it is necessary to consider how many HUBs can exist in serial. The maximum delay between input port and output port is 650ns @2.5Mbps at the TMC2005. It is equivalent to the propagation delay when a cable length is 135m. For example, if every cable length is 10m in Figure 12, the longest distance is physically 50m but it is electrically 590m because of multiplying 10m by 5 and 135m by 4, and the total propagation delay becomes 2.8uS. For analyzing the network timing, consider the delay caused by HUBs. In the ARCNET protocol, it is defined that the longest distance between nodes is the maximum 6.4Km. For example, if 20 TMC2005s exist between nodes in the longest distance, the actual cable length is 3.7Km because of deducting 135m by 20 in converting to cable length from 6.4Km.

		TMC2005						TMC2005						TMC2005					TMC2005
	Port 1 Port 2 Port 3 Port 4 Port 5						Port 1 Port 2 Port 3 Port 4 Port 5						Port 1 Port 2 Port 3 Port 4 Port 5					Port 1 Port 2 Port 3 Port 4 Port 5
1		2	3	4	5	1		2	3	4	5	1		2	3	4	5	1	2	3	4	5
	NODE																					NODE
						FIGURE 12 - CASCADE CONNECTION OF 4 HUBS

Two examples of eight ports HUBs using two TMC2005s are shown in Fig. 13 and 14. If connecting as in Fig. 13, eight TMC2005s exist between the nodes at both far ends. On the other hand, when assigning two ports for cascading connection to the same TMC2005, the number of TMC2005 in serial connection can be down to the number of HUBs plus two, which can reduce the propagation delay.

SMSC TMC2005-JT Page 23 Revision 1.1 (07-24-07)

DATASHEET