EQUAL TO EVALUATQ SUBSET

BACKGROUND

[0001 A fiuidio die is a component of a fluid ejection system that includes a number of fluid ejecting nozzles. The die can also include other non-ejecting actuators such as iero-recireulafion pumps. Through these nozzles and pumps, fluid, such as ink and fusing agent among others, is ejected or moved. Over time,- these nozzles and actuators can become clogged; or otherwise inoperable. As a specific example, -ink in a printing device can, over time, harden and crust This can block the nuzz e and interrupt the operation of subsequent ejection events, Other examples of issues affecting these actuators include fluid fusing on an ejecting element particle contamination, surface puddling, and surface damage to die structures. These end other scenarios may adversely affect operations of the device in which the fluid ic die is installed.

BRIEF DESCRIPTIO OF THE DRAWING ^' S

[0002 The accompanying drawings illustrate various examples of the principles described herein and are part of the specification. The illustrated examples are given merely for illustration, and do not limit the scope of the claims,

[0003] Fig, 1 is a diagram of a fluidic die with a primitive size greater than or equal to an evaluate* subset, according to an example of the principles described herein. [00041 Fig, 2 is a diagram of a fiuidic die with a primitive size greater than or equal to an e aluate subset, .according to another example of th principles described, herein,

O 05] Fig. 3 Is a diagram of a fiuidic die with a primitive size greater than or equal to an ©valuator subset, according to another example of the principles described herein.

0006} Fig, 4 is a flow chart of a method for controlling fluid actuators, according to an example of the principles described herein.

0007J Fig. S is a. flow chart of a method for controlling fluid actuators, according to an example of the principles described herein.

10000] Throughout the drawings, identical referenc numbers designate similar, but not necessarily identical, elements. The figures are net necessarily to scale, and the size of some parts may he exaggerated to more clearly illustrate the example shown, Moreover, the drawings provide examples and or implementations consistent with the description; however, the description is not limited to the examples and/or implementations provided in the drawings.

DETAILED DESCRIPTIO

[0009] Fiuidic dies, as used herein, may describe a variety of types of integrated: devices with which small volumes of fluid may be pumped, mixed, analyzed, ejected, etc. Such fiuldic dies may include ejection dies, such as printheads, additive manufacturing distributor components, digital titration components, and/or other such devices with which volumes f fluid may be selectively and controiiably ejected, Other examples of fiuidic dies include fluid sensor devices, lab-on -a-chip devices, and/or other such devices in which fluids may be analyzed and/or processed.

[0010] in a specific example, these fiuidic systems are found In any number of printing devices such as InkJet printers, multi-function printers (MFPs), and additive manufacturing apparatuses. The fiuidic systems in these devices are used for precisely, and rapidly, dispensing small quantifies of fluid. For example, In an additive manufacturing apparatus, the fluid ejection system dispenses fusing agent The fusing agent is deposited on a build material, which fusing agent facilitates the hardening of build materia! to form a three- dimensional product.

[0011] Other fluid election systems dispense ink on a two-dimensional print medium such as paper. For example, during Inkjet printing, fluid is directed to a fluid ejection die. Depending on the content to be printed, the device in which the fluid ejection system is disposed determines the time and position at which the ink drops are to be released/ejected onto the print medium. In this way, the fluid ejection die releases multiple ink drops over a predefined area to produce a .representation of the image content to fee printed. Besides paper, other forms of print media may aiso be used,

00121 Accordingly _: as has been described, the systems and methods described herein may be Implemented in ^' two-dimensional printing, i.e., depositing fluid on a substrate, and in three-dimensional printing, i>e. _; depositing a fusing agent or other functional agent on a material base to form a three- dimensional printed product,

[0013] Returning to the fluid actuators, a fluid actuator may be disposed In a nozzle, where the nozzle includes a fluid chamber and a nozzle orifice in addition to the fluid actuator. The fluid actuator in this case may be referred to as an ejector that, upon actuation, causes ejection of a fluid drop via the nozzle orifice,

[0014] Fluid actuators may also be pumps. For example, some fiuidic dies include microfluldic channels. A mlerofluidle channel Is a channel of sufficiently small size (e.g. , of nanometer sized scale, micrometer s¾ed scale, millimeter sized scale, etc) to facilitate conveyance of small volumes of fluid (e.g., plooHter scale, nanoilfer scale, microliter scale, milliter scale, etc), Fiuidic actuators may be disposed within these channels which, upon activation,, may generate fluid displacement in the mtcrofluidic channel.

[001 S] Examples of fluid actuators Includ a piezoelectric membrane based actuator, a thermal resistor based actuator, an electrostatic membrane actuator, a mechanical/impact driven membrane actuator, a ntagneto-strietive drive actuator, or other such elements that may cause displacement of fluid responsive to electrical actuation. A fluidic die may include a plurality of fluid actuators, which may be referred to as an array of fluid actuators,

$00163 The array of fluid actuators may be formed into groups referred to as "primitives: ⁸ A primitive .generally includes a group of fluid actuators thai each have a unique actuation address. In some examples, electrical and fluidic constraints of a fluidic die may limit which fluid actuators of each primitive may be actuated concurrently for a given actuation event; Therefore, primitives facilitate addressing and subsequent actuation of fluid ejector subsets that may be concurrently actuated for a given actuation event. A number of fluid ejectors corresponding to a respective primitive may be referred to as a size of the primitive,

[00171 To illustrate by way of example, if a fluidic die has four primitives, each respective primitive may have eight respective fluid actuators {the different fluid actuators having an address 0 to 7), in other words, each fluid actuator within a primitive: has a unique in-primitive address. In some examples, electrical and fluidic constraints limit simultaneous actuation- to one fluid actuator per primitive. Accord ngly, a total of four fluid actuators (one from each primitive) may be concurrently actuated for a given actuation event. For example, for a first actuation event, the respective fluid actuator of each primitive having an address of 0 may be actuated. For a second actuation event, the respective fluid actuator of each primitive having an address of 1 may be actuated .

$0018| A fluid actuator controller facilitates the actuation of the actuators.

For example, a fluid actuator controller may include an actuation data register and a mask register. The actuation data registe stores actuation data that indicates fluid actuators to actuate for a set of actuation events. The mask register stores mask data that indicates a subset of fluid actuators of the array of fluid, actuators enabled fo actuatio for a particular actuation event of the set of actuation events. Accordingly, the fluid actuator controller facilitates concurrent actuation of different arrangements of fluid actuators based on the mask data of the mask register, In some examples, the mask data groups fluid actuators, and tlwaby defines the primitives, [0019] At different points in time, the mask data may change, such that the fluid actuator controller facilitates variable primitive sizes, For example, for a first actuation event, fluid actuators may be arranged in primitives of a first primitive size; as defined by first mask .data stored in the mask register, and for a second actuation event, second mask dat may be loaded into the mask register such that fluid actuators may be arranged in primitives of a second primitive size.

[002QJ White such fluid ejection systems and dies undoubtedly have advanced the field of precise fluid delivery, some conditions Impact their effectiveness. For example, the actuators on a die are subject to many cycles of heating, drive bubble formation, drive bubble collapse, and fluid

replenishment from a fluid reservoir. Over time, and depending on other operating conditions, the actuators may become blocked or otherwise defective. As the process of depositing fluid on surface is a precise operation, these blockages can have a deleterious effect on prifti quality, if one of these fluid actuators fail, and is continually operating following failure, then it may cause neighboring actuators to fail,

[0021] Accordingly, the present specification is directed to a fluidic die that 1) determines the state of a particular fluid actuator and 2) allows for varying the primitive size.- That is, the present specification describes a die wherein a certain number of fluid actuators are coupled to an actuator evaiuator to determine a state of the actuator. However, an actuator evaiuator evaluates one actuator at a time. Accordingly, as the primitive size can vary, if the primitive size is smaller than the number of fluid actuators coupled to an actuator evaiuator, if ma be possible that multiple actuators■ coupled to an actuator evaiuator may be selected for ©valuation. For example, given a primitive size of 3 having addresses 0, 1, and 2, and given four actuator coupled to an actuator evaiuator, it could be possible that two actuators, having address 0 from a first primitive, and having an address 0 from the second primitive, would foe triggered for evaluation, which would lead to a malfunction of the fluidic die.

[0022] Accordingly, the present specification describes a fluidic die that overcomes this, and other complications. Specifically, the present specification

S describes a fiuidic die that includes primitives having at least a threshold number of fluid actuators. Next, the number of fluid actuators that is coupled to an actuator evaiuator is set to be equal to or less than the .primitive size, in so doing, it can be ensured that no more than one fluid actuator per actuator evaiuator is evaluated at a time,

£0023] Specifically, the present specification describes a fiuidic die. The fiuidic die Includes an array of fluid actuators grouped into primitives, An actuator evaiuator of the fiuidic die is coupled to a subset of the array of fluid actuators and a fluid actuator controller of the fiuidic die groups multiple fluid actuators of the array of fluid actuators into primitives, In this example, a primitive size is greater than o equal to a threshold size and the subset of the array of fluid actuators coupled to the actuator evaluation device is less than or equal to the threshold primitive size,

[00241 i another example, a fiuidic die includes an arra of fluid actuators grouped into, primitives and a number of actuator sensors to receive a signal indicative of a state of a fluid actuator. Each actuator sensor is coupled to a respective fluid actuator. The fiuidic die also includes an actuator evaiuator coupled to subset of the array of fluid actuators. The actuator evaiuator evaluates an actuator state of any fluid actuator within the subset and generates an output indicative of the actuator state,. A fluid actuator controller groups multiple fluid actuators of the array into primitives, in this example, a primitive size, is greater than or equal to a threshold size, the subset of the array of fluid actuators coupled to the actuator evaluation device is less than or equal to the threshold primitive size, and primitive sfee varies,

[0025] The present application also describes a method, According to the method, a quantity of fluid actuators within a subset of an arra of fluid actuators that are coupled to an actuator evaiuator is determined, A minimum primitive size set, which minimum primitive size is greater than or equal to the quantity of fluid actuators within the subset. A fluid actuator of the primitive is then activated to generate a first voltage measured at a corresponding fluid actuator sensor and a state of th fluid actuator Is evaluated at the actuato evaiuator based on a comparison of the first voltage and a threshold voltage. e [0026] in one example, using such a fluidic die 1} allows for actuatorevaluation circuitry to be included on a die as opposed to sending sensed signals to actuator evaluation circuitry off die; 2} Increases the efficiency of bandwidth usage between the device and die; 3} reduces computational overhead for the device in which the fluid ejection die is disposed; 4) provides improved resolution times for malfunctioning actuators; 5) allows for actuator evaluation in one primitive while allowing continued operation of actuators: in another primitive; and 6} places management of nozzles on the fluid ejection die as opposed to on the printer in which the fluid ejection die is installed, and 7} accommodates for variation in primitive size. However, it is contemplated that the devices disclosed herein may address other matters and deficiencies in a number of technical areas,

[00271 As used in the present specification and in the appended claims, the term "actuator ^* refers a nozzle or another non-ejecting actuator. For example, a nozzle, which is an actuator, operates to eject fluid from: the fluid ejection die, A recirculation pump, which is an example of a non-ejecting actuator, moves fluid through the fluid slots, channels, and pathways within the fluid ejection die< 0028] Accordingly, as used in the present specificatio and In the appended claims, the term "nozzle" refers to an individual component of a fluid ejection die that dispenses fluid onto a surface. The nozzle includes at least an ejection chamber, an ejector, and a nozzle orifice.

[00291 Further, as used in the present specification and in the appended claims, the term "fluidic die" refers to a component of a fluid ejection system that Includes a number of fluid actuators. Groups of fluid actuators are categorized as "primitives' ^* of the fluidic die, the primitive having a size referring to the number of fluid actuators grouped together, in one example, a primitive size may be between 8 and 16, The fluid ejection die may be organized first into two columns with 30-150 primitives per column.

[0030] Still further, as used in the present specification and i the appended claims, the term "actuation event ^" refers to a concurrent actuation of fluid actuators of the fluidic die to thereby cause fluid displacement. [0031 ] Even further, as used In the present specification and in the

appended claims, the term "a number of or similar language is meant ^' to be understood broadly as any positive number Including 1 to infinity,

[00321 Turning now to the figures, Fig, 1 is a diagram of a fiuidic die (100) with a primitive ( 10) size greater than or equal to a fluid actuator (106} subset, according to an example of the principles described herein. As described above, the fiuidic die (100) is part of a fluid ejection system that houses components for ejecting fluid and/or transporting fluid along various pathways. The fluid that Is ejected and moved throughout the fiuidic die (100) can be of various types including ink, biochemical agents, and/or fusing agents. The fluid actuators (106) may be arranged as an array (102). While Fig.. 1 depicts 12 fluid actuators (108-1 106*2, 106-3, 106-4, 08-S, 106-6, 10 7, 106-8, 106-9, 106-10, 108-11, 06-12} In the array (102), an number of fluid actuators (106) may be formed on the fiuidic die (100). Within the figures, the indication refers to a specific instance of a component. For example, a first fluid actuator is identified as (106-1}. By comparison, the absence of an indication ' refers to the component in general. For example, an actuator In general is referred to as a fluid actuator (106).

10033 The fluid actuators (106) ma be of varying types, For example, the fiuidic die (100) may include an array of nozzles, wherein each no zle includes a fluid actuator (108) that is an ejector. In this example, a fluid ejector, when activated, ejects a drop of fluid through a nozzle orifice of the nozzle.

[0034] Another type of fluid actuator (108) is a recirculation pump that moves fluid between a nozzle channel and a flui slot that feeds the nozzle channel. In this example, the fiuidic die Includes an array of microfluidlc channels. Each microfluidlc channel includes a fluid actuator (106) that is a fluid pump. In this example, the: fluid pump, when activated, displaces fluid within the microfluidlc channel. While the present specification may make reference to particular types of fluid actuator (106), the fiuidic die (100) may Include any number and type of fluid actuators (106).

P>35] The fiuidic die (100} also includes an array of actuator ©valuators (104). Each actuator evaluate* (104-1, 104-2, 1Q4-3, 104-4} is coupled to subset of the array {102} of fluid actuators (106). For example, a first actuator evaluato (104-1) is coupled to a subset that includes a first through third fluid actuates (106-1 , 08-2, 108-3), Following this example, the second actuator ©valuator (104-2). is cou led to the fourth through sixth fluid actuators (108-4, 106*5, 108-8), the third actuator evaluator (104-3) is coupled to the seventh through ninth fluid actuators (106-7, 106-8, 106-9), and the fourth actuator evaluator (104-4) is coupled to the tenth through twelfth fluid actuators (106-10, 106-1 i. 106·· 12).

fOQSSj The actuator ©valuators (104) evaluate a. state of any fluid actuator (106) within the subset that pertains to that actuator ©valuator (104} and generates an output indicative of the fluid actuator (108) state. For example, the first actuator evaluator (104-1 ) can evaluate a state of any of the first fluid actuator (106-1), the second fluid actuator (106-2), and the third fluid actuator ; 106-3).

00371 The fiuidie die (100) also Includes a! fluid actuator controller (1 OS) to group multiple fluid actuators (106) of the array of fluid actuators (106) Into primitives (11.0); Note that the primitive ( 0) grouping may not align with the group of fluid actuators (106) that are coupled to an actuator ©valuator (104), As described above, a. primitive (110) refers to a grouping of fluid actuators (106), where each fluid actuator (106) within the primitive (110) has a unique address, in Fig. 1, the unique address of each fluid actuator (106) is indicated. For example, within the first primitive ( 10-1), the first fluid actuator (108-1) ha an address of 0, the second fluid actuator (108-2) has an address of 1, the third fluid actuator ( 06-3) has an address of 2, and the fourth fluid actuator (106-4) of the primitive (110-1) has an address of 3. Similarly, the fluid actuators (108) that are grouped into the second and third primitive (110-2, 110-3) respectively, have similar addressing,

10038] A quantify of fluid actuators (106) within the primitive (110) thai can he concurrently fired ma be designated. For example, it may be designated that in a given primitive (110), one fluid actuato (106) is enabled at a time,

[00391 At all times, the number of fluid actuators (106) in a primitive (110), which may be referred to a the .primitive ( 10) size, is greater than or equal ^' to a

0 threshold value. This threshold size is greater than or equal to the subset of fluid actuators {106} that is coupled to an actuator evaluator (104). Far example, as described above, the primitive size may vary. However, a lower limit Is set for the primitive (1 0) size. This lower limit may he greater than or equal to the numbe of fluid actuators (108) that are grouped with a ^' .particular actuator evaluator (104). In so doing, it can be assured that no more than one fluid actuator (106) per actuator evaluato (104) is evaluated at a given time,

[0040] For example, if the threshold number is four, then a primitive (1 10) size may be greater than or equal to four and the number of fluid actuators (106) grouped with a particuiar actuator evaluator (104) would be four or fewer. This reduces the chance of fiuldlc di (100} malfunction. For example, if the number of fluid actuators (106) coupled to an actuator evaluator (104) was greater than the threshold, for example five, there Is a chance that multiple fluid actuators (106) per actuator evaluator (104) could be activated for evaluation, which would lead to fluidio die (100) malfunction,

[0041 j For example, suppose the addresses for fluid actuators in the primitives (110) is 0, l _t 2, and 3, and five fluid actuators (108) are paired with each actuator ©valuator (104), there is a possibility, that a fluid actuator (106-1) with address 0 from a first primitive (110-1 ) and an actuator (106) with an address 0 from a adjacent primitive (110-2) may both be selected for evaluation, and both may be coupled to the first actuator evaluator (104-1), Evaluati ng multiple fluid actuators (106) at a lime may be beyond the capabilities of the actuator avaluators ( 04}, and therefore would result in a malfunction of the actuator evaluator ( 04).

10042] By comparison, If the number of fluid actuators (106} coupled to an actuator evaluator (104) is less than to or equal to the threshold as depicted In Fig. 1 , for example three, there is no chance that multiple fluid actuators (108) coupled to a particuiar actuator evaluator (1041 will be evaluated at the same time as long as no more than one fluid actuator (108} per primitive (110) is actuated for a particuiar actuation event.

[0043] In this example, less than all of the actuator evaluafors (104) may be active at given time. For example, if those fluid actuators (108) having an address of 1 are selected for evaluation, then the third actuator ©valuator (104- 3} would be inactive, as it is not grouped with a fluid actuator (106) having a "1 ^s address.

[0044] Accordingly, a Muidic die (100) that has the quantity of fluid actuators (106) coupled to a single actuator ^valuator (104) being less than or equal to the lower limit threshold primitive (110) size, assures that, regardless: of the primitive (110) size, which may change, at most a single fluid actuator (106) per actuator ©valuator (1 4} will be processed for ©valuation.

£00451 Fig, 2 is a diagram of a fluidic die (100) with a primitive (Fig. 1 , 110) s\ greater than or equal to a fluid actuator (Fig. 1 , 106) subset, according to another example of the principles described herein, Specifically, Fig. 2 depicts the fluid actuator controller (108) and on subset of fluid actuators (Fig, 1 , 108) coupled to an actuator ©valuator ( 04). While Fig. 2 depicts two structures, primitive (Fig, 1 , 110) may include any number of structures, in Fig, 2, fluid flow throughout the fluidic die (100) is indicated by the arrows,

[0046] As described above, the fluid actuators (Fig. 1 , 108) may take many forms. For example, the fluidic die (100) ma include a pluralit of nozzles, where each noia e includes an ejection chamber, a nozzle orifice (224), and a fluid actuator (Fig, 1 , 106) in the form of a fluid ejector (226), A shown, each nozzle may be fluidiy connected to a fluid supply (218) via a fluid input (230), in addition, each nozzle may be fluidiy connected to the fluid supply (218) via a microfluidic channel (220) in which a fluid actuator (Fig, 1 , 106) in the form of a fluid pump (222) Is disposed,

[00471 In this example, fluid is conveyed to- the ejection chamber of each nozzle via the respective fluid input (230-1 , 230-2). Actuation of the fluid ejectors (226-1 , 228-2) of each nozzle may displace fluid in the ejection chamber in the form of a fluid drop ejected via the nozzle orifices (224-1, 224-2). Furthermore, fluid may be circulated from the ejection chamber back to the fluid supply (218) via microfluidic channels (220-1, 220-2) by operation of the fluid pumps (222-1 222-2) disposed therein.

[0048] Accordingly, in such examples actuation of the fluid actuators (Fig. 1 , 106) (e.g. , fluid ejectors (226) and fluid pumps (222)) is carried out by the fluid actuator controller (108). in this example, the fluid actuator controller {108} Includes components to manage the actuation of the various fluid actuators {Fig. 1 , 106), For example, the fluid actuator controller (108) Includes an actuation data register (212) and a mask register (214),

00 93 The actuation data register (212) stores actuation data thai indicates each: fluid actuator (Fig, 1 , 106) id actuate for a ser of actuation events. The mask register (214) stores mask data that indicates fluid actuators (Fig. 1, 108} of the array enabled for actuation for a pa iicu actuation event of th set of actuation events. That is, th mask register (212) indicates a set of particular actuation event of the set of actuation events.

[OOSO The fluid actuator controller (108} also includes actuation logic {21.6}, The actuation logic (216} is coupled to the actuation data register (212) and the mask register (214) to determine which fluid pumps (222) and fluid ejectors (226) to actuate for a particular actuation event. The actuation logic (218) is also coupled to the fluid pumps (222) and fluid ejectors (228) to electricall actuate those fluid actuators (Fig. . 106) selected for actuation based on the actuation data register (21 ) and the mask register (214).

Once a particular fluid actuator (Fig. 1 , 106), i.e., fluid pump (222) or fluid ejector (226), has been activated, a corresponding sensor {228-1 , 223-2, 228-3, _. 228-4} collects information regarding the state. For example, in a drive bubble detection system, the sensors (228-1 , 228-2, 228-3, 228-4) detect a voltage, and pass the corresponding voltage to the actuator ^· ©valuator (104) for state determination. That is, the actuator ©valuator (104) can determine a state, for example failing or operational, of any fluid actuator (Fig. 1 , 106) coupled thereto. Note, that as depicted in Fig. 2, in some examples, the actuator sensors (228) are uniquely paired with a corresponding fluid actuator (Fig. 1, 106}.. I.e _> , fluid pump (222) and/or fluid ejector (226) and that a single actuator evaluate-!- (104) is shared among all the fluid actuators (Fig. 1, 106) within the subset,

[00521 The actuator ©valuator (104} Includes various components to determine a stat of the fluid actuato (Fig. 1 , 106). For example, the actuator evaluator ( 04) may Include a compere device (234) to compare an output of an actuator sensor (228) coupled to a respective- fluid actuator (Fig. 1 , 108} against a threshold value to determine when the respective fluid actuator (Fig, 1, 108} is malfunctioning. That is, the compare device (234) determines whether the output of the actuator sensor (228} _; ίίο, is greater than or less than the threshold voltage, ¾ The compare device (234) then outputs a Sign l Indicative of whichs greater,

[G0S3] The output of the compare devic (234) may then foe passed to a storage device (238) of the actuator evaluator (104), in one example, the storage device (236) may be a latch device that .stores the output of the compare device (234) and selectively passes the output. on. While Fig, 2 depicts th storage device (238) In the actuator evaluator (104). In some examples, the storage device (236) may be disposed elsewhere, tor example on a line leading out of the actuator evaluator (104).

[0 δ4| In some examples, the output line (238) is a shared fin© along which outputs of multiple actuator evaiuators (104) are passed. That Is, the output Sine (238) may be a single w re or bus of wires that is connected to all actuator evaiuators (1 4), This output line (238) may b coupled to a sample device. In this example, the actuator evaiuators (104) are controlled such that one actuator evaluator (104) actively drives its sample voltage on the output line (238) at a time. Still further, the sample device (250) receive and stores the sample voltage at the appropriate time,

00SSJ The output line (238) may transmit various pieces of information regarding, a state of the evaluated fluid actuator (Fig. 1 108). in one example, just an output of the actuator sensor (228) is passed along the output line (238) and a. subsequent controller may includ components to associate a particular actuation event with the- corresponding evaluation event. That is, ther is a built In delay between actuation o? a particular fluid actuator (Fig.. 1, 108) and evaluation of that fluid actuator (Fig, 1 , 108). This delay may be on the order of 10 microseconds. However, other fluid actuators (Fig. 1 , 08) may be actuated multiple times during that delay. Accordingly, to ensure accurate evaluation, there should be an association ^' between an actuation and the evaluation ^• resulting from the actuation. Accordingly, the output line (238) may pass just the evaluation results, and a subsequent controller may perform calculations to determine the association.

£80563 tn another example, in addition to passing th evaluation results, th output line (238) may pass an identification of the actuator (Fig. 1, 6) that was evaluated, !n other words, the actuato eva!uator (104} associates the state of the fluid actuator (Fig. 1 , 106) with an address of the fluid actuator (Fig, 1 _: 106), In this example, a downstream controller would not have to perform the calculations to determine the association.

[00571 Fig.. 3 is a diagram of a fluidic die (100) with a primitive ( 1 D) size greater than or equal to a fluid actuator (106) subset, according to another example of the principles described herein. Specifically, Fig, 3 depicts the fluid actuator controller {108} and multiple primitives (110-1 110 -2, 110-3} and multiple actuator ©valuators (104-1 , 104-2, 104-3, 104-4), In this example, the fluidic die ( 00) includes an array of actuator sensors {228} to receive a signal indicative of a state of a corresponding fluid actuator (106). As depicted in Fig. 3, each actuator sensor (228) Is coupled to a respective fluid actuator (106). That is, the actuator sensors (228) sense a state of a corresponding fluid actuator (106). As a specific example, the actuator sensors (228) may be drive bubble detectors that, detect the presence of a drive bubble within an ejection chamber of a nozzle,

[0058] A drive bubble is generated by a fluid actuato (106) to move fluid. For example, in thermal Inkjet printing, a thermal ejector heats up to vaporise a portion of fluid in an ejection chamber. As the bubble expands, it forces fluid out of the nozzle orifice (Fig , 2, 224), As the bubble collapses, a negative pressure within the ejection chamber draws fluid from th fluid feed slot of the fluidic die (100). Sensing the proper formation and collapse of such a drive bubble can be used to evaluate whether a particular fluid actuator (Fig. 1. 08} is operating as expected. That is, a blockage in the nozzle will affect the formation of the drive bubble. If a. drive bubble has not formed as expected, it can be determined that the nozzle is blocked and/or not working In the Intended manner.

[0059] The presence of a drive bubble can be detected by measuring Impedance values within the ejection chamber at different points in time. Thai _s ^' as the vapor that makes up the drive bubble has a different conductivity than the fluid that otherwise ^' is disposed within the chamber, when a drive bubble exists in the ejection chamber, a different impedance value will be measured. Accordingly, a drive bubble detection device measures this impedance and outputs a corresponding voltage,. As will be described below, this output can be used to determine whether a drive bubble is properly forming and therefore determining whether the corresponding nozzle or pump is in a functioning or malfunctioning state. This output can be used to trigger subsequent fluid actuator (108) management operations. While description has been provided of an Impedance measurement, other characteristics may be measured to

determine the. characteristic of the corresponding fluid actuator (108).

[0080] The drive bubble detection devices may include a single electrically conductive plate, such as a tantalum plate, which can detect impedance of whatever medium Is within the ejection chamber. Specifically, each drive bubble detection device measures an impedance of the medium within the ejection chamber, which impedance measure can indicate whether a drive bubble is present in the ejection chamber. The drive bubble detection device then outputs a first voltage value indicative of a state, i.e., drive bubble formed or not, of the corresponding fluid actuatPf (108), This output can be compared against a threshold voltage to determine whether the fluid actuator (100). is

malfunctioning or otherwise inoperable.

[0061] As described above, in some examples such as that depicted In Fig, 3, each actuator sensor .(228) of the number of actuator sensors (228) may be coupled to a respective fluid actuator (106) of the number of fluid actuators (106). in one example, each actuator senso (228) Is uniquely paired with the respective actuator (106) .

[0082J Fig, 3 also depicts the fluid actuator controlle (108), in this example, the fluid actuator controller (108) includes components to manage the actuation of the various fluid actuators (108), For example, the fluid actuator controller includes an actuation data register (212) and a mask register (214),

[00631 The actuation data register (212) stores actuation data that indicates each fluid actuator (106) to actuate for a set of actuation events, For example, the actuation data register (212) may include a set of bits (340-1 through 340- 12) to store actuation data, where each respective bit (340-1 through 340-12) of the actuation data register (212) corresponds to a respective fluid actuator (108- 1 through 106-12). The actuation data register (212) indicates each fluid actuator (106) to actuate for a set of actuation events. For example, for those fluid actuators (108) that are to b actuated fcr a set of actuation events, the corresponding respective bit (340-1 through 340-12) can be set to For those fluid actuators (106) that are not to be actuated for the set of actuation events, th corresponding respective bit (340- through 340-12) can be set to "Q * in the example depicted i Fig. 3, ail of the fluid- ctuators (106) have been activated for a set of actuation events as indicated by each having the respective bit (340-1 th re ugh 340-12) value set to . ;'

[0064) The mask register {214) stores mask data that indicates fluid

actuators (108) of the array enabled for actuation for a particular actuation event of the set of actuation events. That is, the: mask register (214) indicates a set of fluid actuators (108) of the array that are actively enabled for actuation for a respective actuation event of the set of actuation events. For example, for those fluid actuators (108) that are to be actuated for a particuiar actuation event, the corresponding respective bit (342-1 through 342-12) can be set to - 1 For those fluid actuators (10(3) that are not to be actuated for the particular actuation events, the corresponding respective bit (342-1 through 342-12) can he set to "0." In so doing, the mask register (214) configures the size of the primitives (110). That is, the mask register (214) identifies the first fluid actuator (108-1), a fifth fluid actuator (106-8), and a ninth fluid actuator (106-9) to be activated for a particular actuation event. Accordingly, the primitive (110) sisa is established by the mask register (214) to be four fluid actuators. Note that over time, the primitive {110} stee may change based on the information presented in the mask register (214). That is the primitive size ( 10) is not fixed.

[0085] In this example, a threshold for the minimum primitive size (1 0) ma be set. For example, the minimum threshold size may be 4, as depicted in Fig. 3, This threshold size Is based on the number of fluid actuators ( 06) that are grouped to corresponding actuator evaluators (104), For example, the

18 hreshoid size is equai to or greater than the number of fluid actuators (108) thai are grouped to the sctuaior evaluate (104). Doing so ensures that there will at, most be one fluid actuator (108) selected per actuator ^valuator (104) to be evaluated,

[0088] The fluid actuator controller _. (108) also includes actuation logic (216). The actuation logic (216) is coupled to the actuation data register (212) and the mask register (214) to determine which fluid actuators (106) to actuate for a particular actuation event. The actuation logic (216) is also coupled to the fluid actuators (106) to electrically actuate those fluid actuators (106) selected for actuation based on the actuation data register (2 2) and the mask registe (214),

[0067] The fluid actuator controller ( 08) also includes mask control logic (344) to shift mask data stored irs the mask register (214) responsive to the performance of a particular actuation event of a set of actuation events. By shifting the mask data, different fluid actuators (106) are indicated for actuation of a subsequent actuation event of the set of actuation events. To effectuate such shifting, the mask control logic (344) may include a shift count register to store a shift pattern that indicates a number of shifts that are input into the mask register and a shift, state machine which inputs a shift clock to cause the shifting indicated in the shift count register,

[0068] Fig. 4 is a (tow chart of a method (400) for controlling fluid actuators (Fig, 1,· 108), according to an example of the ^■ principles described herein.

According to the method (400), a subset of fluid actuator (Fig. 1, 106) is grouped to an actuator evaluator (Fig. 1 4), and a quantity of fluid actuators (Fig. 1, 106) in that subset Is determined (block 401). As described above, fluid actuators (Fig, 1, 108) are grouped into primitives (Fig, 1, 110) to carry ou printing operations. According to the method (400), a lower limit threshold is set (block 402) for the number of fluid actuators (Fig, 1 , 108) for a primitive (Fig, 1 , 110), Ϊ. .., a lower limit for the primitive (Fig, t 110) size. That is, while the primitive (Fig. 1 , 1 10) size may vary , a lower limit is set such that there are always more, or the same number of, fluid actuators (Fig. 1, 106) in a primitive (Fig. 1 , 110) then there are fluid actuators (Fig. 1 _: 106) associated with an actuator evaluaior (Fig. 1 , 104).

[00691 Next, a fluid actuator (Fig. 1, 06) is activated (block 403). For example, in thermal Inkjet printing, the heating element in a ^■ thermal ejector is heated so as to generate a drive bubble thai forces fluid out the nozzle orifice (Fig. 2, 224). Doing so generates a sense voltage output by the corresponding actuator sensor (Fig. 2, 228), which output is indicative of an Impedance measure at a particular paint in time within the ejection chamber.

[00701 An actuator state is then evaluated (block 404) based at least in part on a comparison of the sense voltage and the threshold voltage, For example, in some cases multiple Instances of a sense voltage are collected and compared against one or more corresponding threshold voltages. The results of the different comparisons are combined to form an actuator signature, which Is used to assess fluid actuator (Fig, 1, 106) health,

[00711 I this example, the threshold voltages may be selected to clearly Indicate a blocked, or .otherwise malfunctioning, fluid actuator (Fig. 1 , 106). That Is, the threshold voltages may correspond to an Impedance measurement expected when a drive bubble is present In the ejection chamber. I.e., the medium in the ejection chamber at that particular time is fluid vapor.

Accordingly , if the medium in the ejection chamber were fluid vapor, then the received sense voltage would be higher than the threshold voltage. By comparison, if the medium: in the ejection chamber is print fluid such as ink. which may be more conductive than fluid vapor, the impedance .would be lower, thus a lower voltage would be present. Accordingly, the threshold voltages are configured such thai a voltage lower than the threshold indicates the presence of fluid, and a voltage higher than the threshold indicates the presence of fluid vapor. If the first voliage is thereby greater than the threshold voltage, it may be determined that a drive bubble is present and If the first voltage is tower than the threshold voltage, It ma be determined that a drive bubble is not present when it should be, and a determination made that the fluid actuator (Fig, 1, 106) Is not performing as expected- While specific reference Is made to output a low voltage to ndicate low impedance. In another example, a high voltage may be output to indicate tow impedance,

[0072] Fig, 5 Is a flow chart of a method (500) for controlling fluid actuators (Fig. 1 , 108}, according to an exam-pia of the prirscipies described herein. In the method <§GG} _:> a quantity of fluid actuators (Fig. 1 108) coupled to an actuator •evaluator (Fig. 1 , 104) determined (block S01) and a lower limit threshold for a primitive (Fig. 1 , 1 10) size is set (block 502) to be greater than or equal to the quantity of fluid actuators (Fig. 106) grouped to an actuator evaluator (fig, 1 104) This may ba done as described above i regards to figure 4.

(0073] A mask register (Fig, 2, 214) is loaded (block 503} with mask data indicating a first subset of fluid actuators (Fig. 1 , 08) to actuate. That is, as described above, the mask register (Fig. 2, 214) includes hits that indicate which of the fluid actuators (Fig. 1 , 108) are enabled for a particular actuation event. Accordingly, this information is loaded into the mask register (Fig. 2, 214). The first subset of fluid actuators (Fig.1 , 106) are then activated (block 504) and a state of a fluid actuator (Fig. , 08} from the first subset is evaluated (block 505) as described above in regards to Fig. 4,

f0G74j Next, the mask data is shifted (block 506) to indicate a different, i,e. , second, subset of fluid actuators (Fig. 1 , 108) to actuate. For example, the mask data may first indicate thai a first, fifth, and ninth actuator (Fig, 1 , 06-1 , 108-5, 108-9) are to be activated. Following this shift, the mask data ma indicate a second subset, for example, a second, sixth, and tenth actuator (Fig, 1, 106-2, 106-6, 106-10) are to be activated. This second subset is then activated (block SO?) and a state of a fluid actuator (Fig. 1 , 100) from the second subset is evaluated (block 508) as described above In regards to claim 4.

[0075] in one example, using such a rluidic die 1) allows for actuator evaluation circuitry to be included on a die as opposed to sending sensed signals to actuator evaluation circuitry off die; 2) increases the efficiency of bandwidth usage between the device and die; .3) reduces computational overhead for the device in which the fluid e ection die Is disposed; 4) provides improved resolution times fo -malfunctioning actuators; 5) allows for actuator evaluation in one primitive while allowing continued operation of actuators in another primitive; and 8) places management of nozzles on the fluid ejection die as opposed to on the printer i which the fluid ejection die is. installed, and 7) accommodates for variation in primitive size, However, it Is contemplated that the devices disclosed herein m address other matters and deficiencies in a number of technical areas.

[00781 The preceding description has been presented to Illustrate and describe examples of the principles described. This description is not intended to be exhaustive or to limit these principles to any precise form disclosed. Many modifications and variations are possible in light of the above teaching.