WO2009150077A1

WO2009150077A1 - Method and an apparatus for reducing the number of operations by a microprocessor for accessing an external memory in automation technology

Info

Publication number: WO2009150077A1
Application number: PCT/EP2009/056729
Authority: WO
Inventors: Alain Chomik; Mathieu Weibel; Elmar Hufschmid
Original assignee: Endress+Hauser Flowtec Ag
Priority date: 2008-06-13
Filing date: 2009-06-02
Publication date: 2009-12-17
Also published as: DE102008028123A1

Abstract

The invention relates to a method for reducing the number of operations by a microprocessor (MCU) for accessing an external memory (SP_ex) for the purpose of displaying an item of information on a display (LCD), wherein the microprocessor (MCU) and the external memory (SP_ex) are associated with the display (LCD) of a two-conductor measuring device in automation technology, wherein the information is composed of different graphical symbols, and wherein the external memory (SP_ex) respectively stores all graphical symbols in the form of a bit map, wherein a subset of the bit maps is stored in an internal memory (SP_in) which is associated with the microprocessor (MCU) and has a predefined number of memory locations, wherein each bit map stored in the internal memory (SP_in) has an associated statistical parameter (Z1) which provides information relating to the frequency with which the corresponding graphical symbol is accessed in a period of time before the current access operation, and wherein the subset is dynamically changed in such a manner that the graphical symbols stored in the internal memory (SP_in) were accessed most often in the period of time before the current access operation, as a result of which the bit maps of the graphical symbols which will also be accessed with a high degree of probability during subsequent access operations are always held in the internal memory.

Description

Method and device for reducing the number of accesses from a microprocessor to an external memory in the

automation technology

The present invention relates to a method and a device for reducing the number of accesses from a microprocessor to an external memory for the purpose of displaying information on a display, the microprocessor and the memory being associated with the display of a two-wire measuring device of the automation technology Information composed of different graphical characters and wherein all the graphic characters are each stored in the form of a bitmap in the external memory.

In automation technology, in particular in process automation technology, field devices are often used which serve to detect and / or influence process variables. Sensors such as level gauges, flowmeters, pressure and temperature measuring devices, pH redox potential measuring devices, conductivity measuring devices, etc., which record the corresponding process variables level, flow, pressure, temperature, pH or conductivity, are used to record process variables. To influence process variables are actuators, such as valves or pumps, via which the Durchfiuss a liquid in a pipe section or the level can be changed in a container. In principle, field devices are old devices which are used close to the process and which supply or process process-relevant information. In addition to the sensors and actuators mentioned above, field devices are generally also those units which are connected directly to a field bus and serve to communicate with the higher-level units. To mention in this context, for example, remote f / Os, gateways, linking devices, etc. A variety of such field devices is manufactured and distributed by the company Endress + Hauser. In modern industrial plants, field devices are generally connected to higher-level units via bus systems, such as Profibus®, Foundation® Fieldbus, HART®, etc. Usually, the higher-level units are control systems or control units, such as a PLC (Programmable Logic Controller) or a PLC (Programmable Logic Controller). The higher-level units serve, among other things, for process control, process visualization, process monitoring and commissioning of the field devices. From the company Endress + Hauser a corresponding operating system under the name FieldCare is offered and distributed.

As already mentioned above, the method according to the invention relates to field devices which are fed via a bus or via a two-wire line. Such field devices are often referred to as two-wire fiddlers and are characterized in that both the communication or the measured value transmission between the field device and the higher-level unit and the power supply of the field device from the parent unit forth via the same common two-wire connection. It goes without saying that Bus- or Zweileitergespeiste

Field devices, in contrast to four-wire field devices, where communication and power supply via separate pairs of conductors, have to make do with relatively little energy.

The energy supply proves to be particularly problematic via a two-wire line if part of the 'intelligence' is outsourced to a display arranged separately from the field device, a so-called SmartDisplay with its own microprocessor and memory modules. Such displays are used when a plurality of graphic characters for the display of information on the display must be maintained. This is especially the case if the display is to be able to display information in different languages. To emphasize is in this Related to the large number of Chinese characters required to display information in Chinese.

The invention has for its object to propose a method and a device that reduce the energy consumption for the presentation of information on a display.

The object is achieved with respect to the method in that the number of energy-intensive accesses from the microprocessor to the external memory is reduced as follows: In a microprocessor-associated internal memory with a predetermined number of memory locations, a subset of the bitmaps that are stored in the external memory are available, stored; each of the bitmaps stored in the internal memory or in the cache is assigned a statistical parameter which gives information about the frequency of accesses to the corresponding graphic character in a period preceding the current access; the subset of the bitmaps of the graphic characters held in the internal memory is dynamically changed such that the graphic characters stored in the internal memory are most frequently accessed in the period preceding the current access. As a result, the bitmaps of the graphic characters are always maintained in the internal memory, which will be accessed with high probability even for subsequent accesses.

According to a development of the method according to the invention, a counter is used as the statistical parameter which is counted up for each current access to the corresponding graphic character.

Furthermore, it is proposed that the internal memory is assigned a pipe with a predetermined number of memory locations, in each of which a statistical index is stored which provides information about it which graphic character that is not stored in the internal memory or in the cache has been accessed softly in the period preceding the current access.

A development of the method according to the invention provides that, in the event that a graphic character is requested by the microprocessor, it is checked whether it is available in the internal memory and, if this is not the case, whether it is available in the pipe, and wherein in the presence of the graphic character in the internal memory or in the pipe, the numerator of the statistical parameter or the statistical index is counted up.

In the event that the currently requested graphic character is not present in the internal memory / cache or in the pipe, it is checked whether a memory space in the internal memory or in the pipe is free. In the event that there is free space, the currently requested graphic character is stored in the internal memory or in the pipe.

For the failure that all memory locations in the internal memory and in the pipe are occupied by graphic characters, according to one embodiment of the method according to the invention, a pipe flush is carried out, the counters of all statistical parameters and the counters of the statistical indices are decremented, and wherein the graphic character (s) are removed from the internal memory or pipe whose counter (s) has a minimum value. Preferably, the minimum value is set to zero.

In addition, it is provided that in the case of a free memory space in the internal memory, the corresponding bitmap of the graphic character is read from the external memory, which is assigned in the pipe as the statistical index of the highest counter, and that a currently requested graphic character, the neither in the internal memory nor stored in the pipe, on the freed space in the pipe with the corresponding statistical index is stored.

In the case of free space in the pipe, the currently requested graphic character, which is listed neither in the internal memory nor in the pipe, is stored in the vacated space in the pipe with the corresponding statistical index.

A preferred embodiment of the method according to the invention provides that the maximum counter of the statistical parameters of the internal memory and the maximum counter of the statistical indices of the pipe are predetermined in such a way that a desired high dynamic in the occupancy of the memory locations is achieved.

Furthermore, it is proposed that the maximum counter of the statistical indices be chosen smaller than the maximum counter of the statistical parameters of the internal memory.

In the event that all memory locations of the internal memory and the pipe are free, the free memory spaces of the internal memory are always occupied first.

A preferred device suitable for carrying out the method according to the invention in its previously described embodiments provides that a main electronics associated with the measuring device and a display electronics associated with the display are provided. Furthermore, in the Display Eiektronik the microprocessor is provided, which is associated with the internal memory and the external memory.

Furthermore, in the external memory, the bitmaps of all graphic characters of different languages are stored, which can be displayed on the display unit of the display. In abstract terms, the invention describes a possibility of saving energy in a two-wire field device. This is achieved via a method or via a device which manages the data flow between the main electronics of the field device, the display and the memory elements on the display itself.

To minimize energy consumption, energy-intensive actions are kept as short as possible and executed as rarely as possible. For two-line powered displays, the respective running or operating time of the microprocessor and reading from the external memory are among the most energy-intensive actions.

As previously mentioned, if large amounts of bitmaps are available, it is necessary to store them on the display in an external memory. If a bitmap is now to be displayed, then this is read from the external memory and displayed on the display, e.g. an LCD - Liquid Crystal Display - written. Bitmaps can be, for example, letters, numbers or characters. The display of a bitmap in the prior art usually always has a memory access to the consequence.

As a display often needs to display sentences or numbers, it requires frequent access to the external memory. In order to reduce the number of accesses, graphic characters frequently used according to the invention are recognized and stored internally. As a result, the number of accesses and thus the power consumption can be considerably reduced.

The method according to the invention remembers the most frequently used characters and keeps them in the fast and energy-saving RAM or internal memory. In order to get the best possible efficiency, there is always a dynamic statistic about a limited before the current access created period. This is necessary to be able to react quickly to different applications, languages and changing masks.

The invention will be explained in more detail with reference to the following figures. It shows:

1 shows a schematic representation of an embodiment of the device according to the invention,

Fig. 2 is a sketched representation of the contents of the internal memory and the external memory and

3 shows a flowchart which clarifies the mode of operation of the method according to the invention.

Fig. 1 shows a schematic representation of an embodiment of the device according to the invention. The main electronics μP is assigned to the field device F. Deposed from the field device F is the SmartDisplay. Field device F and SmartDisplay are supplied with energy via a two-wire line L. The SmartDisplay has a microprocessor MCU to which an internal memory SP ₁₁₁ and an external memory SP ^ are assigned. Over the data lines DL1, DL2 are data between the

Microprocessor MCU and the external memory SP _ei exchanged. On the

Display LCD to be displayed characters are transmitted via the data line DL3. Fig. 2 shows a sketched representation of the contents of the internal memory SP ₁₁₁ and the external memory SP ^. The internal memory SP ₁₁₁ is in two

Divided areas:

- the cache and - the pipe.

The internal memory SP ₁₁₁ stores the graphic characters in the form of

Bitmaps and for each graphic character a statistical, dynamically variable parameter Z1, which provides information about the frequency of the respective graphic character.

The pipe contains statistical indexes Z2 over other frequently occurring graphic characters. Internal memory SP ₁₁₁ and Pipe are limited in the number of memory locations so that they can only accommodate a subset of the graphic symbols stored in the external memory SP _n .

As the statistical parameter Z1 or as the statistical index Z2, each graphic character in the internal memory SP ₁₁₁ and in the pipe contains one

Counter which is incremented each time the graphic character is called. For the time being, non-indexed graphical characters are not taken into account.

If a graphic character or element is requested from the external memory SP _ei , it is first checked whether it is available in the internal memory SP _1n or in the pipe. If this is the case, the Z counter Z is incremented. If this is not the case, it is checked whether there is still free space in the pipe or in the internal memory SP ₁₁₁ . If a memory space is free, the graphic character or the information about the graphic character is stored in the internal memory SP ₁₁₁ or in the pipe. If there is no space left, a so-called pipe operation is performed. This means that the statistical parameters or the statistical indices are decremented by one counter. Subsequently, graphic characters whose counter is zero are removed from the internal memory SP _1n or from the pipe. Occurs by repeated if necessary

If a free space in the internal memory SP ₁₁₁ or in the pipe decrements, the requested graphic character is stored and newly recorded in the internal memory or in the pipe.

The attached pipe creates an intelligent "learning curve" over time, the dropout from the pipe or from the internal memory SP ₁₁₁ depends on the number of accesses to the currently not internal

Memory SP ₁₁₁ or in the pipe existing graphical characters. To keep the lean curve dynamic, the counters in the internal memory SP _1n and in the pipe are each limited by a maximum count.

To avoid a constant change of graphic characters from the internal memory SP ₁₁₁ into the pipe and vice versa, the maximum

Counter of Päpe a much lower value than the maximum counter of the internal memory SP ₁₁₁ .

Fig. 3 shows a Abiaufdiagramm which illustrates the operation of the inventive method. The individual method steps shown in FIG. 3 are illustrated by a specific example, namely the representation of the information 'T e s t T e x t', in steps 1-9.

At the start time, it is assumed that the internal memory SP ₁₁₁ and the pipe are both empty. In the case illustrated below, the internal memory SP ₁₁₁ has only four memory slots for the clarity Bitmaps and the statistical parameters Z1 available; the pipe can store four statistical indexes Z2.

The successive occupancy of the internal memory SP ₁₁ , and the pipe in step 1 is as follows:

Memory Pipe

Empty empty

Empty! Eer

Empty empty

In step 2, it is checked with regard to the requested graphic character, here the letter T, whether there is still free space in the cache. Since this is the case, the letter T is stored in the cache and the statistical parameter Z1 is set to 1.

Memory Pipe

Character: T empty Z: 1 Data empty empty empty empty empty empty

Subsequently, in step 3, it is checked whether there is still room in the cache. Because this is the FaI! is, the letter e is stored in the cache and the counter Z1 is set to 1.

Storage

Sign: T

Z: 1 data

Characters: e empty Z: 1 Data empty empty empty empty

Step 4 checks to see if the letter s is in the cache and there is still room in the cache. Since s is not yet stored in the cache and there is still free space available, the letter s is stored in the cache and the statistical parameter or counter Z1 is set to 1.

Cache pipe

Characters: T empty Z: 1 data

Characters: e empty Z: 1 data

Characters: s Empty Z: 1 Data empty

Analogously as before, the procedure is repeated with the letter t in step 5.

Subsequently, it is checked at step 6 whether there is still room in the cache. Since this is not the case, it is checked whether there is still storage space in the pipe. Since this is the case, the space is stored in the pipe and the statistical index Z2 is set to 1.

In step 7 it is checked whether the letter T is stored in the cache. Since this is the case, the statistical parameter Z1 is incremented and set to 2.

In step 8, the requested letter e is used accordingly.

With regard to the letter x, the following checks are carried out in step 9:

- Is x in the cache? No

- Is there enough space in the cache? No

- Is there room in the pipe? Yes

- Store x in the pipe and set the corresponding statistical index Z2 to 1

In step 10, it is recognized that the letter t already exists in the cache. The counter Z1 is incremented accordingly and set to 2.

To explain an exchange of characters between the cache and the pipe, it is assumed below that at a given time, the cache and pipe have the following occupancy:

If the letter p is requested, it is determined that the letter p is in the pipe and the statistical index Z2 or the counter is incremented and set to 5. It then checks to see if it's in the cache is a graphic character having a lower statistical parameter Z1 or counter than 5. This is the case with the letter s. Now the letter p is stored in the cache and the letter s in the pipe.

To explain a so-called flush, it is assumed below that at a given time, the cache and pipe have the aforementioned occupancy. If a letter r or a graphic character is requested which is neither in the pipe nor in the cache, a so-called flush occurs. The following is checked:

- is the letter r not in the cache? No

- For the flush, all counters Z1 in the cache and in the pipe are decremented, ie counted down by one counter.

- All graphic characters that have a zero in the counter are deleted.

- Save the letter r, because by deleting the character f a Piatz in the pipe has become free.

The cache and pipe occupancy is as follows:

This mechanism results in a two-wire field device saving at least 15% of the energy consumption of the entire SmartDisplay.

Claims

claims

A method of reducing the number of accesses from a microprocessor (MCU) to an external memory [SP _n ]

Representation of information on a display (LCD), the microprocessor (MCU) and the external memory (SP _C ,) the display

(LCD) of a two-wire measuring device are assigned to the automation technology, wherein the information is composed of different graphical characters and wherein in the external memory (SP _n ) all the graphic characters are each stored in the form of a bitmap, wherein in a microprocessor (MCU) associated internal memory (SP ₁₁₁ ) with a predetermined number of memory locations, a subset of the bitmaps is stored, each bitmap stored in the internal memory [SP ₁₁₁ ] is assigned a statistical parameter (Z1), which provides information about the frequency of accesses to the corresponding graphical characters are present in a time period prior to the current access, and wherein the subset is dynamically changed such that the graphic characters stored in the internal memory (SP ₁₁₁ ) have been accessed most frequently in the period preceding the current access, whereby always the bitmaps of the graphic pointer hen in the internal

Memory are accessed, which is accessed with subsequent accesses with a high probability.

2. The method of claim 1, wherein as a statistical parameter (Z 1), a counter is used, which is counted up for each current access to the corresponding graphic character.

3. The method of claim 1, wherein the internal memory (SP ₁₁₁ ) a

Pipe with a predetermined number! of memory locations is assigned, in each of which a statistical index or a second counter (Z2) is stored, which provides information on which graphical

Characters not stored in the internal memory (SP ₁₁₁ ) at which frequency has been accessed in the period preceding the current access.

4. The method according to claim 1 or 2, wherein in the event that of the

Microprocessor (MCU) is requested a graphic character, it is checked whether it is available in the internal memory {SP ₁ J and - if this is not the case - if it is available in the pipe, and wherein in the presence of the graphic character in the internal Memory (SP ₁₁₁ ) or in the pipe of the counter of the statistical parameter (Z1) or the statistical index (Z2) is counted up.

5. The method of claim 4, wherein in the event that the currently requested graphic character is not present in the internal memory (SP _1n ) or in the pipe, it is checked whether there is still a memory space in the internal memory (SP _1n ) or in the Pipe is free, and wherein in the case of a free memory space, the currently requested graphic character in the internal memory (SP ₁₁₁ ) or in the pipe is stored.

6. The method of claim 1, wherein in the event that all memory locations in the internal memory (SP ₁₁₁ ) and in the pipe are occupied with graphic characters, a pipe flush or a cleanup of the pipe is made, wherein the numerator of the statistical parameters (Z 1) and the counters of the statistical indices (Z2) decremented, and the graphic characters are removed from the internal memory [SP ₁ J or the pipe whose counters

(Z1, Z2) has a minimum value, preferably zero.

7, The method of claim 6, wherein in the case of a blank

Memory space in the internal memory (SP _1n ) the corresponding

Bitmap of that graphic character is read from the external memory (SP _ex .), In the pipe as the statistical index (Z2) is assigned the highest counter, and that a currently requested graphic character that neither in the internal memory (57? ) is still stored in the pipe, is stored on the vacant space in the pipe with the corresponding statistical index (Z2).

8. The method according to claim 6, wherein in the case of a blank

Space in the pipe the currently requested graphic character, which is neither listed in the internal memory (SP _1n ) nor in the pipe, is stored on the freed space in the pipe with the corresponding statistical index (Z2).

9. The method of claim 1, wherein the maximum counter (Z 1) of the statistical parameters of the internal memory (SP ₁₁₁ ) and the maximum counter of the statistical indices (Z2) of the pipe are predetermined so that a desired high dynamics in the occupancy of the Memory locations is reached.

10. The method according to claim 9, wherein the maximum counter of the statistical indices (Z2) is chosen smaller than the maximum counter of the statistical parameters (Z1) of the internal memory (SP ₁₁₁ ).

11. The method of claim 1, wherein in the event that all memory locations of the internal memory (SP ₁₁₁ ) and the pipe are free, first the free memory locations of the internal memory (SP ₀₁ ) are occupied.

12. An apparatus for carrying out the method according to one or more of claims 1-11, wherein a device associated with the main electronics (uP) and the display (LCD) associated display electronics are provided, and wherein in the display electronics of the microprocessor ( MCU) is provided to which the internal memory (SP _1n ) and the external memory are assigned.

13. The apparatus of claim 12, wherein in the external memory, the bitmaps of all graphic characters of different languages are stored on the display unit of the display (LCD) for

Display can come.