COM20019IP datasheet(48/81 Pages) SMSC

48 / 81 page

DISCONTINUED DATASHEET

NID Register, no microcode is executed, no

tokens

are

passed

this

node,

and

reconfigurations are generated by this node.

Once a non-zero value is placed in the register,

the core wakes up, but the node will not attempt to

join the network until the TX Enable bit of the

Configuration Register is set.

Before setting the TX Enable bit, the software may

make some determinations.

The software may

first observe the Receive Activity and the Token

Seen bits of the Diagnostic Status Register to

verify the health of the receiver and the network.

Next, the uniqueness of the Node ID value placed

in the Node ID Register is determined. The TX

Enable bit should still be a logic "0" until it is

ensured that the Node ID is unique. If this node

ID already exists, the Duplicate ID bit of the

Diagnostic Status Register is set after a maximum

of 6.72S (or 13.44S if the ET1 and ET2 bits are

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

the network already has this ID, the COM20019

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

6.72S 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

COM20019

has

joined

the

network. Once a value is placed in the Tentative

ID Register, the COM20019 looks for a response

to a token whose DID matches the Tentative ID

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 COM20019 allows the user to better manage

the operation of the network through the use of

the internal Diagnostic Status Register.

high

level

the

Reconfiguration

(MYRECON)

bit

indicates

that

the

Token

Reception Timer of this node expired, causing a

reconfiguration

this

node.

After

the

Reconfiguration

(RECON)

bit

the

Status

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

This allows the node to join the network.

COM20019IP датащи(PDF) 48 Page - SMSC Corporation

COM20019IP датащи(HTML) 48 Page - SMSC Corporation

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