TMC2005-JT SMSC Corporation, TMC2005-JT Datasheet - Page 26

• Manufacturer Part Number: TMC2005-JT
• Description: ARCNET 5 Port HUB Controller
• Manufacturer: SMSC Corporation

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.)
Note 1: Noise may cause an endless loop in a ring system, and the network may hang up. Therefore take care of
Example for system hang-up
Example for no hang-up
Note 2: Place a watch dog timer on one of the TMC2005 in at least one ring. To protect from hang-up the detecting
Note 3: Consider that a total of each segment delay time (cable delay, TMC2005 delay, driver delay and receiver
Revision 1.0 (01-30-06)
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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.
delay) between HUBs in a network is less than 5.6uS (@ 2.5Mbps). The maxmimum distance between
HUBs is approximiately 1000m (@ 2.5Mbps).
designing the patterns between TMC2005 and transceiver or cabling of system.
COM20020
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.
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.
TMC2005
FIGURE 16 - RING CONFIGURATION
DATASHEET
COM20020
TMC2005
COM20020
TMC2005
Page 26
TXEN of any port
A
B
Optical Fiber
Optical Transceiver
TXEN
TMC2005
nRST
nRESET
CK
COM20020
CT
SMSC TMC2005-JT