COM90C66 Datasheet, PDF (44/76 Pages) SMSC Corporation – ARCNET Controller/Transceiver with AT Interface and On-Chip RAM

those tokens transmitted by this node).
The RCVACT and TOKEN bits of the Diagnostic
Status Register may help the user to
troubleshoot the network or the node. If
unusual events are occurring on the network, the
user may find it valuable to use the TXOFF bit of
the Configuration Register to qualify events.
Different combinations indicate different types of
problems.
RCVACT
1
1
1
0
0
Table 15 - Diagnostic Bits for Troubleshooting Network Activity
TOKEN
TXOFF
DESCRIPTION
NORMAL RESULTS
1
1
The node is not part of the network. The
network is operating properly without this
node.
1
0
The node sees receive activity and sees the
token. The basic transmit function is
enabled. Network and node are operating
properly.
ABNORMAL RESULTS
0
X
The node sees receive activity, but is not
seeing the token. Perhaps no other nodes
exist on the the network, or some type of
data corruption exists, or the media driver is
not functioning properly, or the topology is
set up incorrectly, or there is noise on the
network, or a reconfiguration is occurring.
0
0
No receive activity is seen and the basic
transmit function is enabled. The transmitter
and/or receiver are not functioning properly.
0
1
No receive activity is seen and the basic
transmit function is disabled. This node is
not connected to the network.
In addition to the Diagnostic Status Register
bits, the COM90C66 contains two pins for direct
connection to LED's. These pins are meant to
immediately provide basic visual information on
board and network activity with decreased
dependence upon software. The COM90C66
contains an internal retriggerable digital one-
shot which allows the nTXLED to light for 726
uS
+/-10%
each
time
the
COM90C66 transmits information. Every time
the host accesses either the internal RAM,
registers, or external PROM, the nBSLED will
light for 400 mS +/- 20%. The sink capability of
both the nTXLED and nBSLED pins is 10mA,
thus allowing direct connection to the LED's to
be supported by the COM90C66. The only
additional components are 500Ω resistors
between the LED's and VCC.
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