Toshiba T300MVi User Manual download pdf (Page 27)

The default timeout time for the RS232 and RS485 ports is 0, which disables

network timeout handling. When nonzero, timeout processing does not begin

until after a valid network packet has been received by the unit on that port. In

the case of Modbus TCP/IP, a “timeout” event will only be deemed to have

occurred when a communication lapse or abnormal socket error takes place

with the specific client device designated by the “Master IP” address: a

communication lapse or abnormal socket error with any other client will not

result in a timeout event.

When the timeout time is nonzero and a communication interruption is

detected, the timeout enable selections for each point are inspected. Those

points that are found to have their timeout enable selections set to “enabled”

will then have their configured timeout values automatically written to their

assigned “source port” objects. This mechanism provides for a flexible set of

device failsafe conditions to be established on a point-by-point basis.

11.3 Point Configuration

As mentioned in section 1, the TOSVERT-300MVi Multiprotocol Ethernet and

Modbus RTU Interface concept revolves around a central “point database”,

containing the value and access characteristics for each network. With respect

to the interface, a “point” is simply an object that defines some sort of network

access, mapping and configuration data, as well as a single “value” attribute

that can be read from or written to by various communication ports or protocols.

The only restriction placed on this “central clearinghouse” concept is that only

one port can autonomously update the point’s value, “mirroring” its designated

object for other protocols to access. What this means is that although any

protocol can read from or write to a point’s internal value, most of the time that

point’s value will simply be mirroring a remote data object that resides on one of

the interface’s subnets (or on the drive into which it is installed). The selection

of what a specific point is to mirror is performed via its “source port” selection.

For example, a point may be configured to contain Toshiba ASD parameter

mapping and Modbus master ID and holding register mapping information.

However, because both of these protocols act as “master” protocols, only one

of them can be allowed to continuously update the point’s value. If both master

protocols were allowed to simultaneously update the point’s internal value, it

would erratically alternate back and forth between the values designated by the

Toshiba parameter and Modbus holding register objects. Any “slave” protocol

(Modbus RTU slave, Ethernet/IP etc.) can read from or write to a point at any

time, but only the protocol designated by the point’s “source port” assignment

will autonomously update the point’s value independent of any other protocol

traffic.

The “source port” designation also determines where a new point value will be

written to when a “slave” protocol writes a new value to the point. For example,

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Toshiba T300MVi User Manual Page 27