CN101673135B

CN101673135B - Output safety setting circuit based on ARM embedding system

Info

Publication number: CN101673135B
Application number: CN2009100950569A
Authority: CN
Inventors: 王剑平; 张云生; 黄红霞; 张果
Original assignee: Kunming University of Science and Technology
Current assignee: Kunming University of Science and Technology
Priority date: 2009-10-14
Filing date: 2009-10-14
Publication date: 2011-07-27
Anticipated expiration: 2029-10-14
Also published as: CN101673135A

Abstract

The invention provides an output safety setting circuit based on an ARM embedding system, which consists of a 74595 expanded circuit, a reset circuit, an ARM micro-controller system output circuit, and the like. The SFTCLK (pin 11) of the 74595 is connected with the GPC5 of an ARM microcontroller; the LCHCLK (pin 12) of the 74595 is connected with the GPC6 of the ARM microcontroller; the RST (pin 10) of 74595 is connected with the output nRESET (pin 2) of a reset chip; the OE (pin 13) of the 74595 is connected with the GPE6 of the ARM microcontroller; and the OE of the 74595 is pulled upwards by R9 simultaneously. The cascading method of the chip of the 74595 comprises the steps of connecting the SDI (pin 14) of the first 74595 chip with the SDO (pin 9) of the adjacent 74595 chip, leading the SDO (pin 9) of the first 74595 chip to be hung in the air, and connecting the SDI (pin 14) of the final 74595 chip with the GPC7 of the ARM microcontroller. The circuit leads the extended output of the 74595 chip to achieve a controllable output state, and can be controlled in the whole course during the electrification process of the system, and the method has greater application values for the application occasions in which the state needs to be controlled in the whole course.

Description

Output safety setting circuit based on the ARM embedded system

Technical field

The present invention relates to electronic information technical field, particularly based on the output safety setting circuit of ARM embedded system.

Background technology

In many Industry Control Application occasions, the embedded system output must meet security of operation and failure to safety principle.The output overall process that is system must be a safety state as can be known, also can guarantee to be output as safe condition when partial fault.At present very extensive based on the Embedded Application of ARM microcontroller, expand when the low-cost input and output of system is the problem that types of applications faces always.Using 74595 carries out discrete magnitude and exports always and be used widely, but owing to begin to carry out the blank runaway condition of about 100 milliseconds of reset times based on the embedded system of ARM microcontroller in system's instruction that powers on, the application of safety requirements is arranged is serious problem to this section out-of-control time to many.This output pin mainly due to arm processor is defaulted as high-impedance state, and after expansion 74595, because the output that 74595 RST and OE connect arm processor, or because the high-impedance state of acquiescence causes 74595 output state at random.

Summary of the invention

The object of the present invention is to provide a kind of output safety setting circuit, overcome the output set safety problem of the discrete magnitude output expansion of ARM microprocessor, be applicable to the occasion that the output safety state is had relatively high expectations based on the ARM micro controller system.

The present invention changes traditional method for designing, utilize the output signal of ARM and low level reset signal the controling and data signal of reset circuit as 74595 chips, RST 74595 receives the output of proprietary reset circuit and is defaulted as high-impedance state in conjunction with the output pin of arm processor, make 74595 output controlled, thereby reach the safe condition requirement of output in microprocessor internal state reset time.Simultaneously 74595 chips are carried out the cascade expansion, every 74595 exportable 8 road discrete magnitude signals, N sheet 74595 chip cascades then have N x 8 tunnel outputs, only need 4 tunnel outputs as the ARM micro controller system, reach the purpose that 4 tunnel outputs expand to N x 8 tunnel outputs like this.

The physical circuit design is as follows:

The present invention is made of 74595 expanded circuits, reset circuit, ARM micro controller system output circuit etc., 74595 SFTCLK (pin one 1) meets the GPC5 of ARM microcontroller, 74595 LCHCLK (pin one 2) meets the GPC6 of ARM microcontroller, 74595 RST (pin one 0) meets the chip output nRESET (pin two) that resets, 74595 OE (pin one 3) meets the GPE6 of ARM microcontroller, and 74595 OE is drawn on the R9 simultaneously.74595 chip cascade method is as follows: the SDO (pin 9) that the SDI of the 1st 74595 chips (pin one 4) is received adjacent 74595 chips, the SDO of the 1st 74595 chips (pin 9) is unsettled, and the SDI of last 1 74595 chip (pin one 4) meets the GPC7 of ARM microcontroller.

MR (pin 3) signal of chip MAX813 of resetting connects reset switch, is used for hand-reset.

The invention has the beneficial effects as follows:

The general input/output port of the S3C44B0X of employing SAMSUNG company of system or the LPC2300 series A RM micro controller system of NXP company, produce the output control signal of GPC5, GPC6, GPC7 and GPE6, adopt the chip generation reset signal nRESET of the MAXIM MAX813 of company chip or other and this chip compatibility.The MAX813 chip produced reset signal after system powered on, GPC5, GPC6, GPC7, GPE6 and nRESET work together to 74595 chips, multichannel output QA, the QB, QC, QD, QE, QF, QG and the QH output that make 74595 chips are at 0 stable state, after reset signal finishes, the ARM microcontroller begins execution command, can export at 0 or 1 state according to multichannel output QA, QB, QC, QD, QE, QF, QG and the QH output of command request 74595 chips.Make like this overall process that system begins from power on can guarantee that all multichannel output QA, QB, QC, QD, QE, QF, QG and the QH state of 74595 chips is controlled, promptly the output of system extension is controlled.

Before normally moving, the program that arrives after the ARM embedded system powers on during this period of time, can make discrete magnitude place security bit.Utilize the input/output signal of the reset signal of ARM embedded system and system to cooperate the output that makes serial parallel pio chip 74595 chips to place as can be known safe output state.Use 74595 chips and carry out the input and output expansion of the discrete magnitude output of system, solve the not enough problem of output pin of ARM embedded system.

Description of drawings

Fig. 1 is the output safety setting circuit synoptic diagram of ARM embedded system of the present invention.

Fig. 2 is the control signal and the Cascading Methods figure of 74595 chips.

Fig. 3 resets the circuit connecting method figure of chip MAX813.

Embodiment

As shown in Figure 1, the output safety setting circuit of ARM embedded system is made of 74595 expanded circuits, reset circuit, ARM micro controller system output circuit etc., 74595 SFTCLK (pin one 1) meets the GPC5 of ARM microcontroller, 74595 LCHCLK (pin one 2) meets the GPC6 of ARM microcontroller, 74595 RST (pin one 0) meets the chip output nRESET (pin two) that resets, 74595 OE (pin one 3) meets the GPE6 of ARM microcontroller, and 74595 OE is drawn on the R9 simultaneously.

Reset circuit provides reset signal nRESET for out-expander and ARM microcontroller.The ARM microcontroller provides control output signals such as GPC5, GPC6, GPC7 and GPE6 for out-expander, out-expander provides system output signal.The quantity of output signal is by the quantity decision of 74595 chips, and every 74595 chip can produce 8 tunnel output signals.

Be illustrated in figure 2 as the concrete signal method of attachment and the methods of attachment such as power supply, chip controls of 74595 chips, that is: the SDI of the 1st 74595 chips (pin one 4) is received the SDO (pin 9) of adjacent 74595 chips, the SDO of the 1st 74595 chips (pin 9) is unsettled, and the SDI of last 1 74595 chip (pin one 4) meets the GPC7 of ARM microcontroller.

Be illustrated in figure 3 as the concrete connecting circuit figure of reset circuit, the generation of reaction reset signal nRESET and the generation of hand-reset signal.MR (pin 3) signal of chip MAX813 of resetting connects reset switch, is used for hand-reset.

After system powers on, reset circuit produces reset signal nRESET, the ARM microcontroller enters reset mode, at this moment can carry out without any instruction, promptly output is not controlled by the ARM micro-controller instructions yet, about about 100 milliseconds of this reset time, in reseting procedure, reset signal nRESET uses on a left side on the 74595 chip RST (pin one 0) of out-expander, simultaneously because the high-impedance state of the GPE6 of ARM microcontroller for giving tacit consent to, because the existence of pull-up resistor R9, make that GPE6 is the high level output state to 74595 chips, GPE6 meets the OE (pin one 3) of 74595 chips, when the OE of 74595 chips is that " 1 " and 74595 chip RST are during for " 0 ", at this moment 74595 chip QA, QB, QC, QD, QE, QF, QG and QH are the output of high resistant " 0 " state, enter reseting period 74595 chips at the ARM microcontroller like this and are output as controllable state.After the reset signal nRESET of reset circuit becomes " 1 ", system's entry instruction running status, at this moment pass through GPE6 set " 0 ", can make output QA, QB, QC, QD, QE, QF, QG and the QH of 74595 chips by GPC5, GPC6, the cooperation of GPC7 sequential logic is one state or " 0 " state, thereby reaches the purpose of system's control.

The microcontroller of ARM embedded system is selected the S3C44B0X of SAMSUNG company or the LPC2300 series of NXP company for use, the serial parallel pio chip adopts 74595 family chips to comprise as 74HC595,74LV595 etc., and the chip that resets adopts the chip of the MAXIM MAX813 of company chip or other and this chip compatibility.

Claims

1. output safety setting circuit based on the ARM embedded system, it is characterized in that constituting by 74595 chip expanded circuits, reset circuit, ARM micro controller system output circuit etc., the SFTCLK pin one 1 of 74595 chips meets the GPC5 of ARM microcontroller, the LCHCLK pin one 2 of 74595 chips meets the GPC6 of ARM microcontroller, the RST pin one 0 of 74595 chips connects the chip output nRESET pin two that resets, the OE pin one 3 of 74595 chips meets the GPE6 of ARM microcontroller, and the OE of 74595 chips is drawn on the R9 simultaneously.

2. the output safety setting circuit based on the ARM embedded system according to claim 1, it is characterized in that: 74595 chip cascade methods are as follows: the SDO pin 9 of the SDI pin one 4 of the 1st 74595 chips being received adjacent 74595 chips, the SDO pin 9 of the 1st 74595 chips is unsettled, and the SDI pin one 4 of last 1 74595 chip meets the GPC7 of ARM microcontroller.

3. the output safety setting circuit based on the ARM embedded system according to claim 1 is characterized in that: MR pin 3 signals of the chip MAX813 that resets connect reset switch, are used for hand-reset.