INFICON STM-1 Thin Film Deposition Monitor - Manual (Page 7)

2.2 Data Access:
The STM1 card is designed to act as a slave, connected to a master via RS-232/485.
Data flow to and from the STM1 is through a database resident on the STM1 card. This section will explain the database, all of
the data items in it (records), and their properties.
The database is a collection of data objects. Each object has a record # (always one byte, from 0-255) and a data value. The record
# is the key used to address a certain record. The combination of the record # and the data value is called a record. Writes to the
database are called updates, and reads from the database are called queries. A query is when the master (device connected to the
STM1 card via RS-232/485) reads a database record. An update is when the master writes to a database record on the STM1 card.
Records are of variable length, depending on the data type.
The database is divided into 3 groups:
Configuration parameters: All members of this group are parameters that are used in the calculation of the Run Time Data.
This group includes properties such as material density, etc, which are necessary to compute thickness.
Run Time Data: All members of this group are updated (by the STM1) every 100ms, based on sensor data and configuration
parameters. This section of the database can be locked. When locked, all record queries are guaranteed to be from the same
measurement cycle. This avoids temporal errors (rate and thickness not from the same measurement cycle, for example).
Utilities: This group provides utility functions, such as zeroing the thickness, setting the analog output voltage, etc.
2.2.1 Configuration Parameters Group:
All members of this group can be updated and queried.
Configuration parameter updates must be committed in order to take affect. See Note 2.2!
In each case:
Uchar is an 8 bit unsigned value (0-255).
Uint is a 16 bit unsigned value (0-65535).
Ulong is a 32 bit unsigned value (0-4,294,967,295).
Double is a 64 bit floating point value, IEEE format; Sign/exponent in most significant bytes, mantissa in least
significant byte.
Configuration Parameters:
Record#
(dec/hex/ascii)
Name Type Description
65/41/A SessId Uchar Session ID. Copied to Runtime data group CfgPrmSSID.
66/42/B Fq Double Xtal start freq. (Hz)
67/43/C Fm Double Xtal min freq. (Hz)
68/44/D Density Double Material density (gm/cc).
69/45/E Zratio Double Material Z ratio. Not scaled or unitized.
70/46/F Tooling Double 1.000 is 100 % tooling (unity).
71/47/G RateReq Double Requested rate (A/S). For Q monitor only.
72/48/H QlvlTrip Uchar Quality threshold, if non 0 and exceeded, xtal fail occurs.
73/49/I SlvlTrip Uchar Stability threshold, if non 0 and exceeded, xtal fail occurs.
74/4A/J Chmods Xmods_class Additional channel mode bits. See Xmods_class description below.
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