JPH0235309B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field] The present invention relates to an image forming apparatus having a computer.

[Prior art]

An electrophotographic apparatus will be explained below as an example.

Generally, a device for automatically obtaining an electrophotographic image includes a means for sequentially forming an electrostatic latent image on a photoreceptor along the rotation direction around the photoreceptor, a means for developing the latent image,
A means for transferring a visible image onto a copying material and a means for cleaning the photoreceptor in order to form an electrostatic latent image on the photoreceptor again are arranged, and operating equipment necessary for processing in each process is operated at a predetermined timing. or stop it.

Further, if an abnormal condition such as a jam occurs in the device, the operating equipment is stopped.

Conventionally, operating devices were started or stopped by counting a predetermined number of pulses, or stopped by detecting a jam.

If you try to execute these controls using a computer, you will need a routine to correctly detect sequentially generated pulses, and a routine to detect an abnormality in order to stop it immediately if an abnormality occurs at any time. will be provided repeatedly on the program.

Therefore, if an attempt is made to execute another process while the routine is being executed, the original process may be delayed, and if an attempt is made to execute a display, the display may flicker.

Here, as a prior art of the present application, an example of generating a timing signal using a computer without an interrupt function will be described with reference to FIGS. 3 and 4.

FIG. 3 is an example of a program for connecting a clock pulse generator to a so-called input terminal (port) of a computer and counting clock pulses on drum rotation by the computer to generate a timing signal. Regarding the execution of this program,
Details are provided in Application No. 51-36614.

FIG. 4 shows a comparison between the operating clock CP' of the computer and the clock pulse CP generated by the rotation of the photosensitive drum, with the horizontal axis being the same time axis. The steps STEP1-1 in FIG. 3 are executed during several clocks from time t ₁ to t ₂ in FIG. 4. The minimum instruction step for executing each step in FIG. 3 is executed in one clock CP'. shall be

By executing STEP 1-1, the number of pulses that determine the process timing, such as 250 pulses indicating the timing of turning on the paper feed plunger, is read from the ROM memory stored in advance and stored in the memory for calculation. At time t ₂ , it moves to STEP 1-2, but since CP=0, it passes STEP 1-2 and moves to STEP
Move on to 3. Then, between t ₂ <t < t ₃ , the process does not proceed to the next step, and steps 1 to 3 are repeated.

At time t ₃ , CP=1, so move to STEP 1-4. Then STEP 1 in several clocks from t ₃ to t ₄
-4, and set the number of clocks set in memory to -1. Furthermore, execute the next STEP 1-5 from t ₄ to _{t 5} , determine whether the subtracted value is 0, and repeat STEP
1-2 Go back. And since CP=1, t ₅
Repeat STEP 1-2 between ~ _t6 . When CP=0 again at time t ₆ , the process moves to STEP 3, and steps 1 to 3 are repeated until time t ₇ . Here, one pulse CP was input between t ₁ and t ₇ , but by executing STEP 1-4 when CP = 1 rises,
This means that one clock pulse has been counted.
In STEP 1-5, it is determined whether the predetermined clock pulses have been counted, and the process continues from STEP 1-1 until the counting is completed.
Repeat steps 1-4. Upon completion of counting, the computer outputs an operating signal for a predetermined operating device (STEP 1-6). For example, a signal that counts 250 clock pulses and turns on the paper feed plunger is output from a specific output terminal of the computer.

In this way, synchronization between the clock pulse CP generated in synchronization with the rotation of the photosensitive drum and the operation of the computer is realized by STEP 1-2 and STEP 1-3.

In this case, a large number of steps for counting clock pulses are required depending on the number of process control elements requiring timing operations, and these step groups are incorporated in a time series in a sequence control program as shown in FIG. Moreover, it is almost impossible to control other operating devices between counting steps.

For example, if a step group for other control is provided between counting steps, the clock pulse cannot be detected during that control, which may cause problems.
Furthermore, if a display step is provided between counting steps, the display may flicker.

In order to prevent this, the detection signal is input to the interrupt port, and the computer's interrupt function is used to instantly execute the above-mentioned detection and other processes with priority, and the original process and other processes are executed promptly. It is possible that As an example of this, in Japanese Patent Application Laid-open No. 50-62644, perforations made on a photoreceptor belt at intervals of one image and perforations made at small intervals among them are detected and various control signals are sent. There are things that form the.

Small-interval perflation forms a timing control signal for one image by counting the resulting pulses, and large-interval perflation forms a signal corresponding to the leading edge of the image. Since the processing is also detected and processed using the computer's interrupt function, control signals can be generated prior to other processing.

However, there are various noise sources inside and outside the device, which may cause the following inconveniences.

That is, noise can cause instantaneous pulses on the input line to the interrupt port. Therefore, in the case of a function that performs interrupt processing in response to a changing portion of an input signal, even if interrupt processing is not required in response to an instantaneous pulse due to noise, such as before the start of sequence control, If the computer is activated, there is a risk that it will execute interrupt processing.

This may result in malfunction or incorrect display.

〔the purpose〕

The present invention prevents malfunctions due to interruption processing due to noise as much as possible before the start of image formation, and increases the reliability of the interruption processing.

〔composition〕

In terms of configuration, the image forming means includes an image forming means, a start signal generating means for starting image formation, and an image forming means starts image forming by the image forming means in response to an image forming start signal (COPY or DHP) from the start signal generating means. a computer that sequentially controls the image forming means in sequence at a predetermined timing; the computer, as a memory, starts image formation in response to an input signal from the start signal generating means and sequentially controls the image forming means; a main program for interrupting the main program, and an interrupt program for interrupting at least one of interrupt processing related to determining the operation timing of the image forming means or detecting an abnormality. It has a memory (ROM) and a save memory (STACK) for saving the address of the main program, and has a first port (K0 or S3) as an input port for inputting at least a signal from the start signal generating means. )
and a second port (IA or IB) for inputting at least one of a pulse signal for determining the operation timing of the image forming means or a signal for abnormality detection, and further comprising: The image formation start signal input to the first port is determined by the main program, and after that determination,
This allows execution of the interrupt program based on at least one of a pulse signal input to the second port or a signal for abnormality detection, and changes in the pulse signal input to the second port in response to a change in a signal for detecting an abnormality; The main program is interrupted when at least one of and then return to the main program according to a predetermined address after execution of interrupt processing in response to a changing part of the signal for detecting the abnormality. It's in the device.

〔Example〕

The operation of the electrophotographic apparatus shown in FIG. 1 will be briefly explained.

A document is placed on a document table that constitutes a document placement surface, and is pressed down by a document pressure plate 10.
01, a moving reflecting mirror 6, a lens 17, and fixed reflecting mirrors 18 and 19. Therefore, the original is moved by the movable reflecting mirror 8 which moves in the direction indicated by the arrow A in the figure together with the illumination lamp 9, and by the movable reflecting mirror which moves in the same direction at a moving speed of 1/2 of this movable reflecting mirror 8. 6, while the optical path length is kept equal, the light is exposed to a slit through a lens 17 and fixed reflection mirrors 18, 19, and is imaged onto a drum 30 having a photoreceptor on its surface. That is, the document is exposed to slit light while being scanned by an optical system (illumination section). The surface of the drum 30 has a photoreceptor whose photoreceptor layer is covered with a transparent insulating layer. becomes positively charged. Subsequently, when reaching the exposure section 16, the original on the original platen glass is illuminated by the illumination lamp 9, and an image is formed on the drum 30 by the movable reflection mirror, lens, and fixed reflection mirror, so that the photoreceptor is exposed to the original image. At the same time, AC static electricity is removed by an AC charger 13 supplied with AC high voltage current from a high voltage power supply.

Next, an electrostatic latent image is formed on the surface of the drum (photoreceptor) by full exposure by the full surface exposure lamp 33 and enters the developing device 31 .

Development is performed by powder development using a sleeve method, and the electrostatic latent image is visualized.

Next, the transfer material is fed from the cassette 21 or 22 by the paper feed roller 24, conveyed by the first roller 25 and second roller 28, the timing roller clutch CL is turned on, the transfer material is temporarily stopped by the roller 29, and the CL is stopped by the registration signal. Turn on roller 29
is rotated and the paper is conveyed again. The registration signal is obtained from a switch RG that detects a specific passing position of the optical system. The switch OHP generates a signal indicating the optical system home position (stop position).

The transferred transfer material comes into close contact with the drum,
A transfer charger 27 transfers the image on the drum onto a transfer material using a positive high voltage current from a high voltage power source. After the transfer is completed, the transfer material is separated from the drum by a separation roller 26, guided to a heat fixing roller 4, and fixed. After being fixed, excess charge is removed by a static eliminator 3, and the material is discharged onto a tray 20 by a discharge roller. Ru. with this,
Copying is completed, while the drum surface (photoreceptor) is cleaned of residual toner on the drum by the pressed blade 11, and the next cycle can be repeated again. The switch DHP generates a drum home position signal and stops the drum at the position where the photoreceptor joint contacts the cleaner 11. 23
Reference numerals a and 23b designate a lamp for detecting the presence or absence of paper in the cassette, and a light-receiving element that receives the light. Reference numeral 2 designates a paper detection lamp and light-receiving element for detecting paper delay and retention therein. Reference numeral 16 denotes a blank exposure lamp, which exposes the photoreceptor to light to eliminate surface potential unevenness when imagewise exposure is not performed. 7 is a fixing motor, 15 is an optical motor, and 14 is a pre-exposure lamp that fatigues the photoreceptor in advance to make it uniform before the process. A clock pulse generator 36 is composed of a plate that rotates in conjunction with the drum and an optical detector that detects holes in the plate.

Figure 2 shows the operation timing of representative equipment necessary for process processing. One pulse is generated from a clock pulse signal generator for each degree of rotation of the photosensitive drum.

In Figure 2, when you turn on the copy button,
Drives the main motor _M1 to rotate the photosensitive drum,
Turn on the full-surface irradiation lamp L ₁ , turn on the DC charger HV ₁ ,
Operate the AC charger HV ₂ and turn on the timing roller clutch CL to operate the timing roller.

Next, at the timing when 250 clock pulses have been counted from the 0° drum home position, the paper feed plunger PL is turned on and paper is fed from the cassette. At the same time, turn off the timing roller clutch CL to once stop the fed sheet. Next, clock pulse for another 50 counts, i.e. from the drum home position.
Turn off the paper feed plunger PL at a timing corresponding to 300 counts. Further, after counting a predetermined number from the next drum home position, the exposure lamp L ₂ and the developing motor M ₂ are turned on, and after a short count, the clutch OP for advancing the optical system is turned on to start exposure scanning. Thereafter, FIG. 2 shows a copying operation performed twice as described above.

FIG. 6 shows the circuit configuration of the embodiment.

μCOM in the figure is a well-known microcomputer as shown in FIG. 7, which shows its internal circuit.
1B is an interrupt port, and 1B is a light receiving element _D3 that generates a drum clock signal and shapes the waveform.
_C1 is connected, and 1A is connected to a trouble detection circuit that occurs in the copying machine.

D ₁ and D ₂ are copy number display, DIS alarm display, Tr ₁ and Tr ₂ are amplification transistors,
COPY is a copy start button, K is a key button from 0 to 9 for setting the number of copies, and DHP is a micro switch for detecting the drum home position. display
D ₁ and D ₂ are connected to segment selection output ports U ₀ to _{U 6} via the driver, motor M ₁ and alarm
DIS etc. are connected to output port F, DHP is connected to port S, and COPY is connected to port K. i is an inverter.

COPY and key input switch are output ports
Scanned by time-shared signals from R ₀ to R ₆ , K ₀
Dynamically input to the input port of ~ _K3 .
The computer reads input signals from the numeric keypad and the copy button and drives the drum motor _M1 . When the drum rotates, the disc PT rotating in conjunction with the drum motor _M1 generates an intermittent optical signal, which is detected by the light receiving element _D3 to generate a drum clock pulse. At the drum home position, when a DHP signal is generated by a cam installed on the drum and its detection switch, counting of 25 drum clocks is started to turn on the paper feed plunger PL. That is, the DHP ON signal to the input port _S3 causes the interrupt port IB to start accepting drum clock pulses. Then, after a predetermined count, the output port
A drive signal is output from _F1 to turn on the paper feed plunger PL, and the constantly rotating paper feed roller is lowered to feed paper. Furthermore, after 50 clocks, turn off the PL,
From the next DHP signal, 100 clock pulses are counted, and in the same manner as above, the plunger OP for driving the optical system is turned on, the optical system is moved, and exposure is started at the same time. In addition, the turning off of these devices and the operation of other operating devices that require timing are similarly controlled.

Here, a computer having an interrupt function applied to the present invention will be briefly described. This is an element diagram of a 4-bit microcomputer, μPD545 manufactured by NEC Corporation, and the functional circuit blocks within it are shown in FIG.

In the figure, ROM and RAM are memories, PAG is a page register for specifying memory groups in ROM,
ROLY is a step counter to specify the memory address within the group, STACK is the save memory,
INSTDEC is a command word decoder from RCM,
_F0 to _F7 are output ports, _Q0 to _Q7 are serial-parallel conversion registers, _R0 to _R7 , _U0 to _U7 are output ports, FA is an arithmetic circuit, ACC is an accumulator,
TR is an auxiliary register, IA and IB are interrupt input ports, _S0 to _S3 are input/output ports, and _K0 to _K3 are input ports. The input/output ports and interrupt ports mentioned above correspond to the ports in the circuit example shown in FIG.

The above-mentioned ROM stores in advance an instruction code program and the number of control clock pulses for sequence control of the copying process.The RAM temporarily stores data necessary for executing process control and sets flags for discrimination. used for.

Instruction code signals are sequentially output from the ROM by the computer clock, and are decoded by the INSTDEC to generate control signals for executing the program in the ROM.

The control operation will be explained using flowcharts shown in FIGS. 8 to 11.

FIG. 8a shows the program up to turning on the main motor.

First, when the power is turned on and the computer starts operating, it specifies a ROM address according to the computer clock, outputs an instruction code, and executes the program in the ROM. In step 2-1, the first bit of register Q, ie, _Q0 , is set. In step 2-2, the 8 bits of this register _Q0 to _Q7 are
Output to R ₀ ~ R ₇ . In step 2-3, the input data to input port K is stored in accumulator ACC.

At this time, R ₀ is output, so if the COPY signal is input, K ₀ determines whether the COPY button is on or not.
Input from Data corresponding to K ₀ to K ₃ is stored in ACC, and the bit corresponding to K ₀ is 1.
Rattles. In the next step 2-4, data specifying the memory address is set in register DP, and in step 2-5, the RAM specified by that register is set.
The ACC data stored in step 2-3 is transferred to address (00), and it is determined in step 2-6 whether the first bit of this data is 1 or not. If 1
If (yes), the next step 2-7 is executed, and the data specifying the output port _F0 is output from the ROM and stored in the register TR. In step 2-8, the output port _F0 is set, and the output of this _F0 turns on the drum drive motor (main motor) via the driver. Further, the lamp L ₁ and each charger D15 are turned on by other output ports.
In step 2-6, if it is 0, the flow from step 2-1 is repeated again.

Next, in FIG. 8a, the drum is started to rotate and the paper is fed first, but the drum home position is confirmed. 8b, the interruption of drum clock counting will be explained using an example in which 250 drum clock pulses are counted and the paper feed PL is turned on.

In step 3-0, after executing the program flow to determine whether the drum home signal has been input to input port _S3 , in step 3-1, the drum home signal is input from the ROM.
250 codes are output and stored in RAM. At step 3-2, flag B in the flag register of the RAM is set (set to 1). Step 3-3
The flip-flop F/F for accepting interrupts at interrupt port IB is set to enable interrupts by drum clock pulses. This makes it possible to prevent erroneous processing due to noise during a time period before which no interrupt is required. Then, in the following step 3-4, a time division signal is output from R ₆ and R ₇ by setting and resetting to switch the digits on the display.
Segment signals are output from U ₀ to _{U 6} and the indicators D ₁ and D ₂ are dynamically lit. This step 3-4 includes steps based on a large number of instruction codes from reading the ROM code to outputting from the output port. The seven light emitting segments D ₁ and D ₂ display a set number when a key is input, and further display a number subtracted by one from that number each time one copy is completed.
The display is a dynamic display that is performed intermittently in this step. At step 3-5, the subsequent state of the flag set in step 3-2 is determined, and if it remains the same, the process waits until the flag is reset. This causes intermittent display. However, if a drum clock pulse occurs during this time,
The rising edge (change part) of the pulse causes F/
F is reset and an interrupt is input. In other words, the program counter at that time depends on the signal received by IB.
The ROM address specified by POLY is saved to STACK, and another specific address (for example,
100). An interrupt routine program as shown in FIG. 9 (step 4 in FIG. 11) is stored from address 100 in the ROM, and is executed at the rise of the drum clock pulse.

Therefore, the program being executed up to that point is interrupted, and in the case of a clock pulse input between steps 3-4 and 3-5, the above-mentioned intermittent display is interrupted and the clock pulse counting program is executed. When the program execution is finished, the address saved in STACK is set to POLY again, and the main program is executed from the next address.

Figure 9 shows the interrupt routine program, in which step 4-1 subtracts -1 from the memory value 250 stored in step 3-1, and step 4-1 subtracts -1 from the memory value 250 stored in step 3-1.
In step 2, it is determined whether the value has reached 0 or not. The drum home signal DHP is detected, and since this is the first drum clock pulse after passing the home position, that is, after the interrupt is enabled, step 4-3 is skipped and the process proceeds to the next step. Step 4-4 "sets the interrupt acceptance F/F" so that an interrupt is applied again when returning to the main program. Then, according to the command at step 4-5, if the drum clock pulse was generated just before the rising edge of step 3-4, the program returns to step 3-4 of the main program.

When the displays D ₁ and D ₂ are operated again and the next clock pulse is input to port IB, the F/F has been set, so the interrupt counting routine is performed again.

Set the clock pulse to 250 while subtracting from 250.
When the subtraction result becomes 0, flag B is reset in step 4-3. Therefore, when returning to the main routine, it passes through steps 3-5.
- Execute step 6 to set output port F ₁ and set paper feed PL.
will be turned on.

In this way, other operating devices L ₁ , M ₂ , OP,
HV ₁ , HV ₂ , and CL are also time-sequentially controlled.

Signal A in FIG. 10 is an output signal of the F/F connected to the interrupt port, and signal B is a clock pulse signal input to IB. The F/F (signal A) is reset by the rise of the clock pulse B signal, canceling the enabled state of interrupts to port IB and prohibiting them. This makes it possible to prevent malfunctions such as the interrupt routine being restarted by a subsequent instantaneous pulse after the rising edge of the clock pulse before the interrupt routine executed by the rising edge of the clock pulse is completed. Further, once the A signal is set by the acceptance command (step 3-3), it is not reset until the rising edge of the B signal is detected. The same applies to port IA.

Also, if interrupt port IA has a higher priority than IB, connect a trouble detector to IA,
Connect the aforementioned clock pulse generator to IB,
When the trouble detector detects an accident within the copying machine, it can immediately issue an alarm or stop the copying machine operation.

That is, the F/Fs of IA and IB are set, and IA and IB are set first.
When an interrupt signal is input to
Execute the ROM program. Therefore, clock pulse signals to IB are not accepted. On the other hand, first IB
When a clock pulse signal is input to the IB F/F
will be reset only. Therefore, when a trouble signal is subsequently input to IA, the copying machine is stopped regardless of whether an interrupt is being applied to IB (counting of drum clock pulses).

The signal indicating the stop position of the DHP, etc. of a recycled movable member such as a drum is not determined by interrupt processing in response to a change in the input signal, but by determining whether the input signal (DHP) is "0" or "1". Since the main program determines the level state of the printer, even if the printer stops at a fixed position after completing the previous copy, sequence control can be promptly restarted from that position.

In addition, the main program determines the input signals necessary for image formation, such as the drum home signal DHP described above and the copy button signal COPY described later, and allows execution of the interrupt program, so interrupt programs can be executed at unnecessary times. Malfunctions caused by interrupt programs can be prevented.

Fig. 11 is a series of flowcharts for executing Fig. 8a, Fig. 8b, and the subsequent steps, including Step 2.
After determining COPY, the F/F of the IA is set in STEP 11, which prevents erroneous processing due to noise before this step, and then executes the steps from step 3 for counting clock pulses described above to finish the copying process. It is a diagram. Accident signal X
occurs at any step during this process cycle, the step is interrupted and the IA-
High-voltage power supply that executes the START interrupt flow
HV ₁ , HV ₂ , heater H, lamp L ² , developer
M ₂ , turn off the drive system OP and turn on the display DIS to move to the end cycle. As a result, the operation of the copying machine (drum motor M ₁ , lamp L ₁ , clutch
CL) off. After taking safety measures against this accident, the alarm DIS is reset by pressing a reset button (not shown).

Here, the accident detection circuit includes a detection circuit for abnormal temperature inside the copying machine (inside the fixing machine) and a paper ignition detection circuit. It is also possible to use a device that detects the absence of transfer paper and developer in the cassette (see Fig. 1, 23a,
b) Furthermore, it is also possible to detect a jam (paper jam) in the transfer paper path or to detect a paper feeding error from a cassette. If a circuit that detects a paper jam or paper feeding error is connected to the interrupt port, the generation of a detection signal will cause the sequence to shift to the post-drum rotation cycle immediately before the end cycle, thereby removing static electricity from the surface of the drum. can be stopped in any state. As an example of a paper jam detection circuit, a timer is activated at the start of paper feeding for a predetermined period of time (timer).
When paper detector 2 (Fig. 1) at the exit of the passage detects paper, it resets the timer, and when it does not detect paper, it outputs a timer output as a detection signal, and when paper does not pass through detector 2 within a predetermined time (other timer). This is possible by using the timer output as the detection signal.

In addition, some paper feeding error detection circuits operate a timer when paper is fed, and when a paper detector (not shown) installed near the paper feeding roller does not operate within a predetermined timer period, the output of the timer is used as a detection signal. .

〔effect〕

As a result, in programs that perform interrupt processing in response to changing portions of input signals, it is possible to determine the signal for starting image formation and perform interrupt processing, so it is possible to perform interrupt processing even if the computer is already activated. Also, the probability of erroneous processing due to instantaneous pulses due to noise during a time period when interrupt processing is not required can be minimized. Therefore, the reliability of the interrupt processing can be improved in a program interrupt processing in response to a changing portion of an input signal.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a copying apparatus according to the present invention, and FIG.
The figure is an operation time chart of the device in Figure 1, Figure 3 is an example flowchart for timing control, and Figure 4 is an example of a flowchart for timing control.
The figure is a time chart of the drum clock and computer clock, Figure 5 is an example of a flowchart for process sequence control according to Figure 3, Figure 6 is an example of a control circuit according to the present invention, and Figure 7 is the μCOM element of Figure 6. 8a, b, and 9 are flowchart examples for sequence control in FIG. 6, and FIG. 10 is a time chart showing the relationship between the flip-flop for interrupt reception and the clock pulse.
FIG. 11 is a further example of a flowchart according to FIG. 6 of the present invention, in which D ₃ is a drum clock pulse generation photodiode, Th is an abnormal temperature detection element, IA and IB are interrupt input terminals, F ₀ to F ₉ are controlled load output terminals.

Claims (1)

[Scope of Claims] 1. an image forming means; a start signal generation means for starting image formation; and a start signal generating means for starting image formation by the image forming means in response to an image formation start signal from the start signal generating means. and a computer that sequentially controls the image forming means in sequence at a predetermined timing, and the computer has a memory that starts image formation in response to an input signal from the start signal generating means and sequentially controls the image forming means. and an interrupt program that interrupts the main program and performs at least one of interrupt processing related to determining the operation timing of the image forming means or detecting an abnormality. and a save memory for saving the address of the main program, and a first port as an input port for inputting at least a signal from the start signal generating means, and a first port for determining the operation timing of the image forming means. and a second port for inputting at least one of a pulse signal for detection and a signal for abnormality detection, and the image forming start signal input to the first port is input to the main program After the determination, execution of the interrupt program is permitted based on at least one of a pulse signal input to the second port or a signal for detecting an abnormality; In response to a changing portion of the pulse signal input to the input device, the address of the program memory is saved in the save memory and the main program is interrupted, or in response to a changing portion of the signal for detecting an abnormality. The main program is interrupted by at least one of the interruptions of the above-mentioned main program, and the interrupt processing by the above-mentioned interrupt program is executed, and after the execution of the interrupt processing in response to the change part of the above-mentioned pulse signal, the above-mentioned save memory The main program is returned to the main program according to the save address stored in the memory, and the main program is returned to the main program according to the predetermined address after execution of the interrupt processing in response to the changing part of the signal for detecting the abnormality. An image forming apparatus characterized by: