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HISTORY CARD

HISTORY CARD
SUPPLEMENT

	"Frames" and "Depth"
	"Frame Numbers" and "Halt Depth"
	"Emptying" Historical Data
	"Dumping" Historical Data
	Playback Time Search
	Calculating Recorder Memory Volume

"Frames" and "Depth"  [Back ]

All of the data-channel and logic-bit readings recorded by one of the History Card's recorders at a given instant of time constitute a FRAME within that recorder's "history" memory.  In other words, each frame corresponds to a single, instantaneous recording of data for all channels and bits that have been entered in the given recorder's "LIST."  Every frame can also include the date of recording, if so specified by the initial LIST (LST) command.

A sequence of frames within a given recorder thus corresponds to a time-correlated sequence of separate recordings of the same set of selected process variables (channels and bits).  A useful analogy, as shown in the following figure, is that of a strip of movie film, each frame of which depicts an instantaneous state of the same continuously changing scene.

One important difference, however, between the sequence of frames for a History Card recorder and for a movie film is that the time increment between successive movie frames is constant, whereas the time that separates any two successive History Card frames in a sequence may or may not be constant, depending on how you have set up the recording process.  Thus, for example, you can instruct a History Card recorder to make recordings at precisely regular time intervals, or you can make it record only upon occurrence of a prespecified combination of system logic, limit, and/or time interval conditions (see the examples of the STORE (STO) command).

Every frame of data within a recorder's memory has an 8-digit SERIAL NUMBER, for the purpose of relating it chronologically to other frames in the recorder.  This number provides a means of verifying not only the precise sequence of multiple recordings (frames), but also the completeness of such a sequence.  It can be used to correlate a given frame with an actual measured entity, like an individual part on a production line or a measured process at a particular moment of time.  For setting and resetting the serial number, see the RESET SERIAL NUMBER (RSN) command.

The DEPTH of a given recorder refers to its frame capacity; the maximum number of frames of data it can hold is its "depth of storage."  This is a variable quantity for each recorder and is defined by the user via the DEPTH (DPT) command (see also "Calculating Recorder Memory Volume," below).  In terms of the movie-film analogy, the depth is simply the number of frames on the film strip, which is of course proportional to the total length of the strip.

To better conceptualize the situation, however, we need to add to our analogy an element that represents the actual recording process.  Let us therefore suppose that our movie film consists initially of "blank" frames.  As the film is advanced (at either a constant or variable rate), each blank frame will successively pass in front of some kind of "imprinting device."  This device will "write" upon that frame the data readings reported by all listed channels and bits at that instant of time.  The situation is illustrated in the following figure.  Note that the farther a particular "written" frame is from the imprinting device, the older in time is the data it contains.

When all of the initially blank frames have been "written" upon—that is, when the recorder's total depth has been reached—then any subsequent recording of data automatically overwrites the oldest frame in that recorder's memory.  To complete our picture, then, we must join the first and final frames of our film, to create a circular band of frames, continuously revolving in time.  Now, each time a "written" frame passes by the imprinting device, it will be erased and then "rewritten" with up-to-date values for all of the recorder's listed channels and bits.

Keep in mind that we cannot speak of an absolutely "first" or "last" frame in the recorder's memory (when "FRAME NUMBERS" are assigned—as explained in the next section—these numbers will always be relative to a predefined "halt-triggering" event).  We can meaningfully speak, however, of the oldest ("written") frame in memory, since all written frames are "time-stamped": each frame corresponds to a particular time of recording.

"Frame Numbers" and "Halt Depth"  [Back ]

The HALT (HLT) command lets you specify the process condition or logical combination of conditions which will cause a given History Card recorder to halt the recording of data.  Syntax for the HLT expression is the same as for the STORE (STO) command (see the examples of the STORE (STO) command).

You may sometimes want the History Card to continue to record a specific number of frames after a "halt-triggering" event has occurred.  The HALT DEPTH (HDP) command lets you arrange for the actual halting of a given recorder to be delayed (after occurrence of a "halt-triggering" event) until a specified number of additional frames have been recorded.  In the figure below, the HALT DEPTH (i.e., the number of frames to be recorded following a "halt-triggering" event before recording actually comes to a halt) is "4."

"FRAME NUMBERS" are used in conjunction with the HISTORY DUMP (HDU) command (discussed below).  Relating recorded frames chronologically to a "halt-triggering" event, these numbers enable you to "dump" a specified number of frames that were recorded before the event and a specified number recorded after the event (up to the predefined "halt depth" of the recorder).

As shown in the above figure, all frames recorded before a "halt-triggering" event are designated by negative numbers.  The larger the negative number, the older the frame.  Thus, the last frame to be recorded prior to a "halt-triggering" event is always given a frame number of "-1."

Frames recorded after a "halt-triggering" event (up to the number of frames defined by the "halt depth") are given by positive numbers.  The smaller the positive number, the older the frame.  thus, the first frame to be recorded following the event is given a frame number of "(+)1."

"Emptying" Historical Data  [Back ]

In general, you will use the EMPTY (EMP) command while recording is in process.  The command allows you to learn what has happened since the last such interrogation.

The EMP command instructs the History Card to output, in sequence, either all frames or a selected number of frames that have been recorded by a given recorder since the last EMP command was applied to that recorder.  When a selected number of frames is emptied, the sequence will start from the oldest frame not emptied by a prior EMP command.

In the following figure, for example, five recorded frames separate the applications of two successive EMPTY (EMP) commands (i.e., EMP' and EMP).  Frame "f1" is the oldest frame not emptied by the command EMP'.  Thus, a present command of

EMP n = 3

will empty Frames "f1," "f2," and "f3" from this recorder (No. n).

The contents of each "emptied" frame will constitute a line of output.  The number of output lines transmitted by the History Card in response to an EMPTY (EMP) command will therefore equal the number of frames recorded or requested, whichever is smaller.  The precise format for each line of output will depend on the last OUTPUT IMAGE (IMA) command to have been applied to the recorder in question (see sample formats).

Despite its name, the EMPTY (EMP) command does not literally "empty" a recorder's frames.  Until the recorder's depth is reached, all recorded frames will remain in its memory, regardless of any and all EMPTY (EMP) commands that may have been applied.  (After its depth has been filled, of course, the oldest frame in the recorder's memory will be lost with each subsequent recording.)  

By applying the REACCESS HISTORY MEMORY (RHM) command, you can restore access to all frames still in storage that have been previously "emptied," or to a specified number of frames recorded prior to the last application of the EMPTY (EMP) command.  For example, if the film strip shown in the above figure represents Recorder No. 2, then a command of

RHM 2 = 3

applied after the command EMP (and before any subsequent EMPTY (EMP) command) will restore for future "re-emptying" Frames "f4," "f5," and "f6."

"Dumping" Historical Data  [Back ]

In general, you will use the HISTORY DUMP (HDU) command after recording has stopped.  As shown in the figure below, HDU serves to define a flexible "history window" that lets you review a specified period of data history.  All recorded frames "seen" through the window are "dumped" as output from the History Card.  Regions of a recorder's history record can be dumped at any time (and not just after occurrence of a "halt-triggering" event); such dumping is not affected by any previously applied EMPTY (EMP) command.

As an example of the HDU command, suppose that recordings are taken by the History Card's Recorder No. 3 at 5-second intervals, as specified by the initial STORE (STO) command.  Suppose also that a "halt depth" of "4" has been specified for the recorder (see above).

The frame numbers associated with the sequence of recordings will be determined by the time at which the predefined "halt-triggering" condition is detected.  In this example, the "halt-triggering" event occurs between times XX:XX:30 and XX:XX:35, and so the frame-number sequence is as shown in the following figure.  Note that four recordings have been made following the "halt-triggering" event, because a "halt depth" of "4" had been indicated for this recorder.

To dump three frames prior to the "halt-triggering" event and two frames following it (as indicated in the above figure), you would command

HDU 3 = -3 to 2

The five frames recorded from XX:XX:20 through XX:XX:40 will consequently be transmitted from the History Card.

As with the EMPTY (EMP) command, each output line will correspond to a single frame, and the precise output format will be determined by the last OUTPUT IMAGE (IMA) command to have been applied to this recorder.

Playback Time Search  [Back ]

The History Card's versatile "playback" function makes available for direct interrogation, monitoring, and/or data display all of the readings that are currently in history memory.  The basis entity is the PLAYBACK CHANNEL, which can be assigned any channel number from 1 through 997 (when the Model 10BSPC384 History SPC Option Card is present, special kinds "STATISTICAL" PLAYBACK CHANNELS may be set up; much of the following discussion, however, applies only to "nonstatistical" playbacks).  A playback channel can be interrogated just like any other system data channel.  It can be continuously monitored for conformance to preset limit values, and can serve as an analog-output source.

With their own channel-number series from 1000 through 1299, VIDEO PLAYBACK CHANNELS are strictly intended for data display of recorded data.  Up to 300 video playbacks can be set up for a given History Card.  These channels can be made to exhibit standard event-controlled visual effects, such as instantaneous color change or flashing (see the general discussion of System 10 Data Display capabilities).  A displayed video playback can also include the serial number, time, or date of a recorded data value.

A playback channel can be set up to represent the data value for a given channel that was either last recorded by a given History Card recorder or recorded a specific number of frames in the past.  Thus, for example, the command

PLA 33 = REC 2, CHN 48 (-5)

creates Playback Channel No. 33 to represent the recording made of Channel No. 48 by Recorder No. 2 five frames "ago."  Here, "5" is the SEARCH DEPTH for Playback Channel No. 33; it is a measure of the "pastness" in time of the frame within the recorder's memory that contains the data reading of interest.  See the following figure.  The allowable search depth can be from 1 through 32767, provided that it does not exceed the total depth predesignated for that recorder.

Note that, as time goes on and new recordings continue to be made, the SEARCH FRAME will "advance" accordingly, since the SEARCH DEPTH (the "pastness" of the search frame) will always remain constant, unless a ZOOM (ZUM) or REPLAY (RPL) command is in effect (see below).

In the above figure, the upper picture represents the state of a recorder "film strip" at a given time; the lower picture represents the same strip at a later time, after another recording has been made.  With the recording of the frame with the SERIAL NUMBER of "7," the SEARCH FRAME automatically moves from "2" to "3," and the data reading reported by the playback channel changes accordingly.  The SEARCH DEPTH, however, remains a constant five frames.

Several useful run-time commands relate to the playback of historical data: ZOOM (ZUM), FREEZE (FRZ), and REPLAY (RPL).

By means of the ZOOM (ZUM) command, you can readily alter the magnitude of the search depth (and hence the current position of the search frame).  In effect, this lets you displace all of a recorder's playback readings backward or forward in time by the same number of recordings.  You can also specify a search-depth offset to be applied simply by pressing the Back Space key (to go backwards in time by that number of recordings) or the Step key (to go forward in time).  The effects of the ZUM command on a single playback channel are illustrated in the following figure.

By means of the ZOOM (ZUM) command, you can rapidly review all the values that have been reported by a complete set of data channels over a complete "historical" period, even while recording is in process.  Specifically, you can use this command to observe how all or part of the data channels contained in a given recorder's "list" have evolved together in time.

FREEZE (FRZ) is a special form of the ZUM command.  It lets you "zoom" to a search frame that does not change with ongoing recordings.  Thus, after initially changing a recorder's search depth by the specified number of frames, FRZ will automatically increase the search depth by one each time a subsequent recording is made.  All of the recorder's playbacks will therefore continue to report the recorded data to which they were originally "zoomed."

The REPLAY (RPL) command is normally applied after recording has stopped.  By successively decreasing the current search depth one frame at a time (until the "latest" frame has been reached), it lets you review—at a selected "replay rate"—all stored recordings for any and all of a recorder's playback channels.  You will designate the time interval (from 10 ms to 20 minutes) at which the replay is to step forward from the oldest recording to the latest.  RPL thus permits "slow motion" playback of all data recorded during a fast event, or a fast review of all data recorded for a test or process of long duration.  If desired, the entire replay process may be indefinitely repeated.

Calculating Recorder Memory Volume  [Back ]

The History Card's normal capacity is 32000 scaled data readings.  The total "history memory" may be extended by means of the optional Model 10BHDM384 High Density History Memory Card (or the Model 10BSPC384 High Density History SPC Option Card).  The portion of the total memory that will be allocated to each of the History Card's four RAM recorders is dependent on the size of that recorders specified "LIST" of variables to be included in each frame of data, multiplied by the specified "depth" (the total number of frames to be recorded).

To determine a given recorder's "LIST" size (L), you should

1. Add the number of "listed" channels and the number of "listed" system bit groups.

2. Add to this sum either "4" (if the DATE is not included in the list) or "6" (if the DATE is included).

3. Round up the resultant sum to the next integral multiple of 8.

To obtain the recorder's required memory volume (V), multiply the recorder's list size (L) by its depth (D):

V = L x D

For example, suppose that the list you have entered for Recorder No. 1 includes 28 selected data channels and 3 selected system bit groups, and also specifies the recording of the system date.  Then the list size L for this recorder equals 28 + 3 + 6, or 37, rounded to the next higher multiple of 8, which is 40.  If the depth of Recorder No. 1 has been set to, say, 150, then the memory required by the recorder (in its presently specified list/depth configuration) is 40 x 150 = 6000 readings.

Naturally, the sum of the four individual recorder memories cannot exceed the total "history memory" of the system.  If it happens that a recorder does not have sufficient memory to make as many recordings of a specified list as are called for by its specified depth, then the system will automatically adjust the depth of the recorder in question and also the depth of every higher-numbered recorder, in order to produce an allowable recorder memory volume sufficient for the entered list.  Lower-numbered recorders are thus given priority for memory space.