Owner's manual

Introduction 1-5
1.4.4 Interleaved Blocks
The Equipment never sends interleaved blocks to the Host. That is, the Equipment always sends all
blocks of one message before sending the first block of the next message. This simplifies the job of the
Host. However, the Equipment allows the Host to send interleaved blocks, if it so chooses.
1.4.5 Simultaneous Transactions
The Equipment may initiate several simultaneous outstanding SECS transactions. That is, the Equipment
may send a secondary primary message before the Host has sent the Reply to a previous primary
message. Mainly, this occurs when the Equipment reports Alarms and Events. The Host can reduce the
number of outstanding transactions initiated by the Equipment by setting equipment constants
appropriately so that the Equipment sends no W-Bit for Stream 5 (Alarm), Stream 6 (Event), and Stream
10 (Free Text) messages.
The Equipment allows the Host to initiate at least two (2) simultaneous outstanding transactions.
1.5 SECS-II Clarifications
The Equipment uses the following SECS-II conventions:
1.5.1 Data Format Types
Where the Standards permit a choice of data item types, the choice has been made as described in
Section 4 - SECS Message Detail.
For outgoing messages, the Equipment always sends Data Items of the exact format shown. For some
incoming messages, the Equipment “forgives” minor Host errors. For example, the Equipment may
accept a U1 Data Item where a U2 format was expected. We recommend the Host attempt to use the
formats shown.
1.5.2 Data Item Length Bytes
For messages sent by the Equipment, the number of length bytes in Data Items is always the minimum
required to contain the Data Item length.
For messages received from the Host, the number of length bytes in Data Items can be 1, 2, or 3,
provided that the length parameter can accurately be specified.
1.5.3 ASCII Data
Unless otherwise specified, all ASCII data items must contain printable ASCII data—that is, characters
in the range 0x20 to 0x7E.
1.5.4 Multi-Block Messages
Wherever the Host is supposed to send a single-block message, this Equipment will also accept multi-
block format.
The maximum size for a single SECS message is approximately 1000 blocks (256,000 bytes).