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GEM Manual for DEK Printers Capabilities Issue 1.6 January 22, 2018 Page 49 of 171 4.10.2 Monitoring Limit Characteristics A limit is defined by a set of attributes that include the variable (VID) to which the limit corr…
GEM Manual for DEK Printers Capabilities
Issue 1.6 January 22, 2018 Page 48 of 171
4.10 Limits Monitoring
The DEK printer is capable of monitoring limits on selected status variables and discrete variables.
These variables are identified in section 5.5. The printer provides seven configurable limits that may
be applied to each variable. When one of these limits is crossed a collection event is generated. The
event can be used to alert the host that the variable has crossed a limit.
4.10.1 Definitions
Limit - Used in this section to represent the set of variable limit attributes that completely describe a
variable monitoring "barrier." The attributes include VID, Units, UPPERDB, LOWERDB,
LIMITMAX, and LIMITMIN. In some contexts it may be interpreted more narrowly as the
combination of UPPERDB and LOWERDB.
LIMITIDn - Refers to the identifier of a specific limit (as defined by UPPERDB and LOWERDB)
among the set of limits for a monitored equipment variable. LIMITIDs are consecutively numbered,
beginning at one through the number of limits possible (seven minimum).
Monitoring Zone - A subset of the possible range of values for a variable of interest to the host. A
single limit divides the range into two zones. Multiple limits may be combined to divide the range
even further.
Zone Transition - The movement of a variable value from one monitoring zone to another. This
transition is a collection event and has a corresponding CEID.
Deadband - An overlap of two zones implemented to prevent constant zone transitions by a variable
sitting on or near a limit (i.e. "chattering").
UPPERDB - A variable limit attribute that defines the upper boundary of the deadband of a limit. The
value applies to a single limit (LIMITID) for a specified VID. Thus, UPPERDB and LOWERDB as a
pair define a limit.
LOWERDB - A variable limit attribute that defines the lower boundary of the deadband of a limit.
The value applies to a single limit (LIMITID) for a specified VID. Thus, UPPERDB and LOWERDB
as a pair define a limit.
UPPER ZONE - The range of values lying above a limit.
LOWER ZONE - The range of values lying below a limit.
LIMITMAX - The maximum value for any limits of a specific equipment variable. This value is set
by the equipment manufacturer and typically coincides with the maximum value allowed for the
monitored variable.
GEM Manual for DEK Printers Capabilities
Issue 1.6 January 22, 2018 Page 49 of 171
4.10.2 Monitoring Limit Characteristics
A limit is defined by a set of attributes that include the variable (VID) to which the limit corresponds,
the units of that variable, the maximum and minimum possible values of the limit (LIMITMAX and
LIMITMIN) and the specific borders of the limit (UPPERDB and LOWERDB).
There is a limitation to the values of UPPERDB and LOWERDB which may be stated as:
LIMITMAX>UPPERDB>LOWERDB>LIMITMIN
Example of how Limits can be applied to monitor a variable:
Limit 1
Limit 2
Limit 3
Limit 4
Limit 5
Limit 6
Limit 7
Nominal
Upper Spec. Limit
Lower Spec. Limit
Upper Control Limit
Lower Control Limit
Minimum Limit
Maximum Limit
A limit divides the possible range of variable values into two parts, the upper zone and the lower zone.
At any time, the monitored variable is considered to be in one and only one of these zones. However,
as these two zones have an area of overlap. This is called the deadband.
UPPER ZONE
LOWER ZONE
DEAD BAND
Event
Event
LIMITMAX
LIMITMIN
UPPERDB
LOWERDB
GEM Manual for DEK Printers Capabilities
Issue 1.6 January 22, 2018 Page 50 of 171
The deadband is a key concept of limits monitoring, especially for floating point variables. Its purpose
is to prevent a phenomenon known as chattering (the repeated changing of zones due to small, rapid
fluctuations in variable value while near the zone boundary). In practice, the value of a variable must
reach the opposite boundary of the deadband before a zone transition can occur. Thus, if a variable's
value reaches the UPPERDB and moves into the upper zone, it will not return to the lower zone until it
falls back to the LOWERDB. The difference between UPPERDB and LOWERDB should always be
greater than the typical amplitude of those fluctuations, which are deemed insignificant. In some cases,
the width of the deadband may set to zero (UPPERDB = LOWERDB). At first glance, this would
seem to make indeterminate the current zone when an integer value sits on the limit. However, this is
not the case, when movement of the value is considered.
To illustrate, an example is given, assuming that UPPERDB = LOWERDB = 100. The list shows
consecutive readings of the variable and the resultant zone:
99 Lower Zone (Initial reading)
101 Upper Zone (Zone transition)
100 Lower Zone (Zone transition)
100 Lower Zone
99 Lower Zone
100 Upper Zone (Zone transition)
Transition from one zone into another generates a collection event, as might be reported via S6F11.
The host has the option of receiving notification by enabling event reporting for the event. For each
variable that has monitoring capability, one CEID is reserved to indicate zone transitions for that
variable. To aid in the determination of the nature of a transition event, three DVVAL's have been
defined: LimitVariable, EventLimit and TransitionType.
Scenarios:
Host defines limit attributes:
Comments Host Equipment Comments
[IF] S2, F45 is Multi-block
[THEN] Send Multi-block inquire
S2F39 -->
<-- S2F40 Multi-block grant.
[END IF]
Host defines new variable limit
attributes
S2F45 -->
<-- S2F46 Equipment acknowledges Host request.
Host queries equipment for current limits:
Comments Host Equipment Comments
Host queries Equipment for current
variable limit attribute definitions
S2F47 -->
<-- S2F48 Equipment returns report containing requested
variable limit attribute values.
Examples of applying limits monitoring for different applications are shown in SEMI E30-95
Appendix 7.