NEC NDA-30115-001 manual 02H ‘1’ ‘!’ ‘L’ 03H, Message Count Range Block Check Code Range

Architecture Property Management System - Communication Interface

The messages (but not the control codes or start sequence) sent between the NEAX and the PMS must have header and trailing sections as defined in the following format:

0 1 2 3 4 6 8 9

02H ‘1’

‘!’

‘L’

...

03H xx

STX SA UA EI FTC MSC FC Message ETX BCC

Message Count Range

Block Check Code Range

Table 2-3 Base Message Format

The message format breaks down as follows:

•STX -- Start of text block. (One byte - 02H.)

•SA -- System Address. (One byte - ‘1’ [31H].)

•UA -- I/O Unit Address. (One byte - ‘!’ [21H].)

•EI -- Entry Index. (One byte - ‘L’ [4CH].)

•FTC -- Feature Code. (See below.) A list is provided in Appendix C, “Feature Codes”.

•MSC -- Message Counter. This represents the length of the message. The count of characters starts at the FTC field and ends at the last character of the body of the message, not including the ETX. If the ETX character does not immediately follow the character specified by the message counter, an invalid message is assumed.

•FC -- Function Code. This specifies the individual operation and processing for the feature designated by the Feature Code (FTC). A list is provided in Appendix D, “Function Codes”.

•ETX -- End of text block. (One byte - 03H.)

•BCC -- Block Check Code. This is computed by an exclusive OR of the message from the SA to the ETX (inclusive). Detection of an STX starts the computation (but the STX is not included). Detection of an ETX stops the computation (and the ETX is included). (One byte.)

Feature Codes range in value from 00 to FF (hex). These codes define the “Major Category Codes” for service features.

Codes from 80 to FF are used as “Violation Codes”. When a specific message received from the PMS cannot be processed for some reason, 80 (hex) is added to the received Feature Code so that it will be handled as a Violation Code. If the NEAX regards a text as a Violation Code, the system data of the NEAX may be assigned so that a text of this type is returned to the PMS. Therefore, when the PMS has received a Violation Code, provisions should be made for the PMS to print out this violation.

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