User guide

Neuron C Programmer’s Guide 123
It might not always be possible to determine rate_est and max_rate_est. For
example, message output rates are often a function of the particular network
where the device is installed. These optional values can be used by a network
tool to perform network device analysis. Although any value in the range
0-18780 can be specified, not all values are used. The values are mapped into
encoded values
n in the range 0-127. Only the encoded values are stored in the
device's self-identification (SI) data. The actual value can be reconstructed from
the encoded value. If the encoded value is zero, the actual value is undefined. If
the encoded value is in the range 1-127, the actual value is:
5)8/(
2
−
=
n
a
rounded to the nearest tenth. The actual value,
a , produced by the formula, is in
units of messages per second.
You must assign a message tag to the msg_out.tag field for each outgoing
message. This specifies which connection point (corresponds to an address table
entry) to use for the outgoing message. After the tag field has been assigned, the
message must be either sent or cancelled.
Besides addressing, message tags are also used for correlating completion events
and responses with outgoing messages. For example, the following when clause
correlates a message completion event with a message sent by means of the tag1
message tag:
when (msg_completes(tag1))
By qualifying an event with a message tag, the event becomes TRUE only when
an event corresponding to that particular outgoing message occurs.
Message Codes
A message code is a numeric identifier for a message. Each application message
must include a message code that the receiving applications can use to interpret
the contents of the message.
Message codes are used by all LonTalk messages, not just application messages.
They fall into the ranges shown in
Table 8. Codes 0-62 and 64-78 are for use by
applications. The lower range is used for proprietary application-specific
messages, and the upper range is used for proprietary application-level gateways
to other networks.
Table 8. Ranges for Message Codes
Type of Message Message Code Description
User Application
Messages
0 to 47
(0x00..0x2F)
Generic application messages. The
interpretation of the message code
is left to your application.
Standard Application
Messages
48 to 62
(0x30..0x3E)
Standard application messages
defined by L
ONMARK
International.