INFICON XTM/2 Thin Film Deposition Monitor - Manual (Page 72)

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XTM/2 Operating Manual
3.8.3 Service Requests and Message Available
In the IEEE mode there are a number of events which will trigger service
requests, a request by the instrument to transmit information to the host. The
instrument does this by triggering the RQS bit of the Status Byte. A host initiated
serial poll then identifies the requesting device by the presence of a 1 in the
RQS (2
6
) bit of the status byte. The particular service request generator event
is encoded in bits 2
0
- 2
3
inclusive, as shown below:
It takes the instrument various lengths of time to formulate a correct response
to queries for information. To avoid unnecessarily repeated bus traffic, it is
suggested that the host monitor the MAV (message available) status bit to
determine when a response for information is fully assembled and ready to
transmit.
Table 3-5 Service Request Encoding
Generator Event Code Value
FINAL THICKNESS 0001 1
STBY/ON sequence 0100 4
Crystal Fail 0110 6
250ms DATA READY. Available only
after R23 is issued, see
page 3-26 .
This is automatically cleared on
crystal failure.
0111 7
TIMER SPT exceeded 1000 8
THICKNESS SPT exceeded 1001 9
2
7
2
6
2
5
2
4
2
3
2
2
2
1
2
0
not
used not
used
Service request
generation encoding
RQS MAV
Result of Serial Poll