CN202711238U

CN202711238U - Watchdog circuit

Info

Publication number: CN202711238U
Application number: CN 201220364727
Authority: CN
Inventors: 鲁灿
Original assignee: Shanghai Feixun Data Communication Technology Co Ltd
Current assignee: Shanghai Feixun Data Communication Technology Co Ltd
Priority date: 2012-07-25
Filing date: 2012-07-25
Publication date: 2013-01-30
Anticipated expiration: 2022-07-25

Abstract

The utility model discloses a watchdog circuit, which comprises a watchdog chip and a switching circuit, wherein the dog feed signal input end of the watchdog chip is connected with a dog feed signal source; the dog feed signal output end of the watchdog chip is connected with a resetting input end of the watchdog chip through the switching circuit; the switching circuit is also electrically connected with a switching control signal source; the switching circuit switches on or switches off the resetting input end and the dog feed signal output end according to a switching control signal generated by the switching control signal source. The watchdog circuit controls switch-on or switch-off between the resetting input end and the dog feed signal output end of the watchdog chip through the switching circuit, so that a function of enabling the watchdog chip can be realized, and a system can automatically switch on the watchdog chip at proper time.

Description

Watchdog circuit

Technical field

The utility model relates to a kind of watchdog circuit, particularly relates to a kind of watchdog circuit that is applicable to embedded system.

Background technology

In the microcomputer system that is consisted of by single-chip microcomputer; the interference of electromagnetic field because the work of single-chip microcomputer usually can be subject to coming from the outside; cause the race of program to fly; and be absorbed in endless loop; the normal operation of program is interrupted; can't be worked on by monolithic processor controlled system; can cause the dead state that is absorbed in of whole system; unpredictable consequence occurs; so for the consideration of the single-chip microcomputer running status being carried out Real-Time Monitoring; just produced a kind of chip that is specifically designed to monitoring Single Chip Microcomputer (SCM) program running status, be commonly called as " house dog " (watchdog).

At present, watchdog chip uses in system in a large number, and its Main Function is that (fly such as race, run and wait indefinitely) resetting system when unusual appears in the software in system, thereby increases the antijamming capability of system, improves its reliability.Watchdog chip mainly comprises hand-reset (MR, Manual Reset) pin, feeds dog input (WDI, WatchDog Input) pin and house dog output (WDO, WatchDog Output) pin.More common using method is that the hand-reset pin MR of watchdog chip connects house dog output pin WDO, feeding dog input pin WDI then generally links to each other with the IO pin of CPU, the software of system is regularly fed this process of dog input pin WDI(with the clear signal input and is called " feeding dog ", show that current running software is normal, correspondingly, house dog output pin WDO output high level; Regularly do not receive clear signal if feed dog input pin WDI, show that current software may run extremely, then house dog output pin WDO is with output low level.Because house dog output pin WDO links to each other with hand-reset pin MR, so that the corresponding generation reset signal of watchdog chip resets to system.

Aforesaid operations is applied to produce effect very much in system's normal course of operation, but be not that system all wishes to see house dog work any moment, for example in the embedded system start-up course, dog can't feed in system, thereby cause system constantly to restart, so generally do not wish to see house dog work this moment.

The utility model content

The technical problems to be solved in the utility model is the defective that can only wait unlatching house dog manual under the state in the prior art in order to overcome after system starts, a kind of watchdog circuit is provided, enable watchdog chip by an on-off circuit, thereby so that watchdog chip can be opened automatically in the suitable time by system.

The utility model solves above-mentioned technical matters by following technical proposals:

The utility model provides a kind of watchdog circuit, comprises a watchdog chip, is characterized in, described watchdog circuit also comprises an on-off circuit;

The feeding-dog signal input end of wherein said watchdog chip connects a feeding-dog signal source, the feeding-dog signal output terminal of described watchdog chip connects the RESET input of described watchdog chip by described on-off circuit, described on-off circuit also is electrically connected with a switch controlling signal source;

The switch controlling signal that described on-off circuit generates based on described switch controlling signal source is so that conducting or shutoff between described the RESET input and the feeding-dog signal output terminal.

Wherein described on-off circuit of the present utility model is used for the RESET input of control watchdog chip and shutoff or the conducting between the feeding-dog signal output terminal, thereby any employing watchdog circuit of the present utility model only needs just to control enabling of watchdog chip by the turn-on and turn-off of gauge tap circuit.

And the source of switch controlling signal described in the utility model can utilize the mode of existing software in the Single Chip Microcomputer (SCM) system or hardware and their combination to realize.

Preferably, described on-off circuit is a buffer chip.

Preferably, described buffer chip is the 74LVC1G126 chip of PHILIPS Co..

Preferably, described watchdog chip is the ADM706 chip of Ya De promise semiconductor company.

Positive progressive effect of the present utility model is:

Watchdog circuit of the present utility model is controlled the RESET input of watchdog chip and shutoff or the conducting between the feeding-dog signal output terminal by an on-off circuit, thereby realize enabling the function of watchdog chip, thereby so that watchdog chip can be opened automatically in the suitable time by system.

Only need in addition a buffer chip to get final product in the utility model, simple in structure, implementation is succinct, and cost is very low.

Description of drawings

Fig. 1 is the structural drawing of the preferred embodiment of watchdog circuit of the present utility model.

Embodiment

Provide the utility model preferred embodiment below in conjunction with accompanying drawing, to describe the technical solution of the utility model in detail.

The watchdog circuit of the present embodiment mainly adopts a watchdog chip ADM706 and the buffer chip 74LVC1G126 with 3 attitudes to form, and as shown in Figure 1, comprises an ADM706 chip U1 and a 74LVC1G126 chip U2 in the described watchdog circuit.

Comprise A end, Y end and OE end among the wherein said 74LVC1G126 chip U2, wherein said OE end and A end are input end, and described Y end is output terminal, and have logical relation as shown in the table between A end, Y end and the OE end.

OE	A	Y
			H	H	H
H	L	L
			L	X	Z

As above shown in the table, the conducting between described OE end control A end and the Y end is namely when the OE end is input as high level, conducting between described A end and the Y end, thus the level of Y section is identical with the level of A end, when the OE end is input as low level, which kind of level no matter the A end input, and the Y end all is in high-impedance state.

The feeding-dog signal input end WDI of the chip of ADM706 described in the present embodiment U1 connects an outside feeding-dog signal source DOG_WDI, the feeding-dog signal output terminal WDO of described ADM706 chip U1 is electrically connected the A end of described 74LVC1G126 chip U2, described ADM706 chip U1 the RESET input MR is electrically connected the Y end of described 74LVC1G126 chip U2, and the OE end of described 74LVC1G126 chip U2 also is electrically connected with a switch controlling signal source DOG_EN.

The switch controlling signal that wherein said 74LVC1G126 chip U2 generates based on described switch controlling signal source DOG_EN, i.e. high-low level signal is so that conducting or shutoff between described the RESET input MR and the feeding-dog signal output terminal WDO.

So the present embodiment is held conducting or the shutoff that has realized between feeding-dog signal output terminal WDO and the described the RESET input MR by A end and Y.Wherein said switch controlling signal source can utilize the mode of existing software in Single Chip Microcomputer (SCM) system etc. or hardware and their combination to realize, therefore at this its specific implementation process is repeated no more.

Other circuit elements device or external power supply etc. shown in Fig. 1 all are ADM706 chip U1 and 74LVC1G126 chip U2 necessary peripheral circuits when normally moving in addition, and the specific implementation that watchdog circuit is realized the function automatically enable is only described in the present embodiment, therefore repeat no more in this specific implementation process to other peripheral circuits.

The specific works principle of the present embodiment is as follows:

When the watchdog circuit of the present embodiment is worked, the 6th pin feeding-dog signal input end WDI of ADM706 chip U1 can receive the feeding-dog signal DOG_WDI from the chip of external microcontroller always, if feeding-dog signal DOG_WDI is normal, this moment, the 8th pin feeding-dog signal output terminal WDO of ADM706 chip U1 can export high level, high level is transferred to the 2nd pin A end input of 74LVC1G126 chip U2, the switch controlling signal DOG_EN control that the control pin OE end of 74LVC1G126 chip U2 can be generated by the chip of external microcontroller, this signal also can be software control, after the normal startup of Single Chip Microcomputer (SCM) system, software can be drawn high this signal, 74LVC1G126 chip U2 conducting this moment, the 4th pin Y end output that is 74LVC1G126 chip U2 namely is the high level of the 2nd pin A end input, after high level is transferred to the 1st pin preset input end MR of ADM706 chip U1, can any change not arranged to the output of ADM706 chip U1, namely Single Chip Microcomputer (SCM) system normal operation this moment does not have reset signal output.

When the 6th pin feeding-dog signal input end WDI of ADM706 chip U1 reception feeding-dog signal is overtime, can be by low level of the 8th pin feeding-dog signal output terminal WDO output, this moment, the 4th pin Y end output of 74LVC1G126 chip U2 also was low level, so the 1st pin preset input end MR of ADM706 chip U1 is input as low level, principle of work according to ADM706 chip U1, this moment, the 7th pin preset signal output part RST of ADM706 can export a low level reset signal RESETN to master chip, so can reset to whole Single Chip Microcomputer (SCM) system, so just finished the action that under the states such as Single Chip Microcomputer (SCM) system deadlock, resets.

Although more than described embodiment of the present utility model, it will be understood by those of skill in the art that these only illustrate, protection domain of the present utility model is limited by appended claims.Those skilled in the art can make various changes or modifications to these embodiments under the prerequisite that does not deviate from principle of the present utility model and essence, but these changes and modification all fall into protection domain of the present utility model.

Claims

1. a watchdog circuit comprises a watchdog chip, it is characterized in that, described watchdog circuit also comprises an on-off circuit;

2. watchdog circuit as claimed in claim 1 is characterized in that, described on-off circuit is a buffer chip.

3. watchdog circuit as claimed in claim 2 is characterized in that, described buffer chip is the 74LVC1G126 chip of PHILIPS Co..

4. such as each described watchdog circuit among the claim 1-3, it is characterized in that, described watchdog chip is the ADM706 chip of Ya De promise semiconductor company.