Solartron Mobrey 3595 4C, User Manual

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Results and Error Formats 3595 4C User Manual Part Two
2-6
35952350 (CH02/AA)
2.4 EVENT RESULT FORMAT
Event results are obtainable only from digital IMP type 3595 2A and switch IMP type 3595 2B, set-up for
‘events capture’. The 3595 2A IMP can store up to 6000 bytes of event data, whilst the 3595 2B can store
up to 512 bytes. Both types can transmit up to 112 bytes of event data at a time.
Event data carries information on the time and directional change of a digital signal. The time of a detected
event is referenced to the IMP internal calendar and clock, which is regularly synchronised from the 3595
4C Interface card. Synchronisation is performed regularly and it does not affect measurement integrity.
Event data is transmitted in Stream 2. If the on-card input buffer for Stream 2 and the relevant IMP is
empty, the event data is transmitted as soon as it occurs. However, if the input buffer already holds unread
data, the IMP stores results and transmits the event data when the buffer is free.
Event data consists of:
Bookmarks . Four bytes containing the calendar month, day, hour and minute.
Event tags . Four bytes containing the channel number, direction of transition, calendar seconds
and milliseconds. One event tags is sent per event.
End tags . Four bytes containing only binary zeroes. This indicates the end of a set of event
data, and is used when less than 112 bytes of event data is transmitted.
Lost event results . When the event storage area of the IMP and on-card input buffer are full, the IMP
has nowhere to send or store event results. Instead, it counts the number of events
that occur. This data is stored in a 4-byte result and loaded into the output buffer
when space is available. Up to 65535 lost events can be counted.
Event data transmitted by an IMP can consist of a number of bookmarks, event tags and one end tag. Only
a single bookmark is sent per calendar minute (and this is only if an event occurs). A bookmark gives the
most significant calendar data for all event tags sent after it, until the next bookmark is sent.
If event data is sent to a free buffer (on the 4C Interface card), data for only one result is sent: this consists
of a bookmark, an event tag and an end tag. Subsequent data is sent only if the application software reads
the initial data. The IMP, whilst waiting for the buffer to become free, stores any new event tags and
bookmarks. This new data is sent when the buffer is free. An end tag is added if the stream of event data
is less than 112 bytes long, but this tag can be replaced by a lost event tag if one is to be sent.
Event status responses also go into Stream 2. In this case, the event tag is replaced by the ‘event status
format’.