ARCNET 5 Port HUB Controller

Datasheet

Ring Network With the TMC2005

The reliability of the network can be improved by connecting every node in a ring, because the communication is maintained through the reverse route even if the cable is cut at a point. However ARCNET controller alone can not support ring, because ARCNET is a half-duplex communication system. Using HUBs makes possible for ARCNET to built a ring network as in Fig.16. This configuration is available only for using fiber optics. (Refer to the application note for details.)

COM20020

TMC2005

Optical Transceiver

A

B

Optical Fiber

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

COM20020

 

TMC2005

 

 

 

 

 

 

 

 

 

 

 

 

 

TMC2005

 

COM20020

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

nRST

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

TXEN

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

nRESET

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

CK

CT

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

TMC2005

 

TXEN of any port

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

COM20020

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

FIGURE 16 - RING CONFIGURATION

Note 1: Noise may cause an endless loop in a ring system, and the network may hang up. Therefore take care of designing the patterns between TMC2005 and transceiver or cabling of system.

Example for system hang-up

-A noise occurs only at “A” point in Figure 16.

-The noise propagates clockwise on the network.

-TMC2005 detects the noise that came back through the ring.

-The noise causes an endless loop in the ring.

Example for no hang-up

-Any noise occurs at “A” and “B” points in Figure 16 at the same time.

-The noise propagates to both directions in the network.

-An endless loop doesn’t occur because TMC2005s in the middle absorb the noise from both sides.

Note 2: Place a watch dog timer on one of the TMC2005 in at least one ring. To protect from hang-up the detecting time of the watch dog timer should be set to longer than 2.7 mS (@ 2.5Mbps) that is the burst time in the ARCNET protocol.

Note 3: Consider that a total of each segment delay time (cable delay, TMC2005 delay, driver delay and receiver delay) between HUBs in a network is less than 5.6uS (@ 2.5Mbps). The maxmimum distance between HUBs is approximiately 1000m (@ 2.5Mbps).

Revision 1.1 (07-24-07)

Page 26

SMSC TMC2005-JT

DATASHEET