COM20022V-HT 查看數據表（PDF） - SMSC -> Microchip

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COM20022V-HT

10Mbps ARCNET controller with 2Kx8 on-board RAM

SMSC -> Microchip 

Diagnostic Status Register is set after a maximum

of 210mS (or 420mS if the ET1 and ET2 bits are

other than 1,1). To determine if another node on

the network already has this ID, the COM20022

compares the value in the Node ID Register with

the DID's of the token, and determines whether

there is a response to it. Once the Diagnostic

Status Register is read, the DUPID bit is cleared.

The user may then attempt a new ID value, wait

210mS before checking the Duplicate ID bit, and

repeat the process until a unique Node ID is

found. At this point, the TX Enable bit may be set

to allow the node to join the network. Once the

node joins the network, a reconfiguration occurs,

as usual, thus setting the MYRECON bit of the

Diagnostic Status Register.

The Tentative ID Register may be used to build a

network map of all the nodes on the network, even

once the COM20022 has joined the network.

Once a value is placed in the Tentative ID

Register, the COM20022 looks for a response to a

token whose DID matches the Tentative ID

Register. The software can record this

information and continue placing Tentative ID

values into the register to continue building the

network map. A complete network map is only

valid until nodes are added to or deleted from the

network. Note that a node cannot detect the

existence of the next logical node on the network

when using the Tentative ID. To determine the

next logical node, the software should read the

Next ID Register.

IMPROVED DIAGNOSTICS

The COM20022 allows the user to better manage

the operation of the network through the use of

the internal Diagnostic Status Register.

A high level on the My Reconfiguration

(MYRECON) bit indicates that the Token

Reception Timer of this node expired, causing a

reconfiguration by this node. After the

Reconfiguration (RECON) bit of the Status

Register interrupts the microcontroller, the

interrupt service routine will typically read the

MYRECON bit of the Diagnostic Status Register.

Reading the Diagnostic Status Register resets the

MYRECON bit. Successive occurrences of a logic

"1" on the MYRECON bit indicates that a problem

exists with this node. At that point, the transmitter

should be disabled so that the entire network is

not held down while the node is being evaluated.

The Duplicate ID (DUPID) bit is used before the

node joins the network to ensure that another

node with the same ID does not exist on the

network. Once it is determined that the ID in the

Node ID Register is unique, the software should

write a logic "1" to bit 5 of the Configuration

Register to enable the basic transmit function.

This allows the node to join the network.

The Receive Activity (RCVACT) bit of the

Diagnostic Status Register will be set to a logic "1"

whenever activity (logic "1") is detected on the

RXIN pin.

The Token Seen (TOKEN) bit is set to a logic "1"

whenever any token has been seen on the

network (except those tokens transmitted by this

node).

The RCVACT and TOKEN bits 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 TXEN bit of the

Configuration Register to qualify events. Different

combinations of the RCVACT, TOKEN, and TXEN

bits, as shown indicate different situations:

Normal Results:

RCVACT=1, TOKEN=1, TXEN=0: The node is

not part of the network. The network is operating

properly without this node.

RCVACT=1, TOKEN=1, TXEN=1: The node sees

receive activity and sees the token. The basic

transmit function is enabled. Network and node

are operating properly.

MYRECON=0, DUPID=0, RCVACT=1, TXEN=0,

TOKEN=1: Single node network.

Abnormal Results:

RCVACT=1, TOKEN=0, TXEN=X: The node sees

receive activity, but does not see the token.

Either no other nodes exist on the network, some

type of data corruption exists, the media driver is

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