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Driving method of photoelectric isolation parallel-in-serial-out circuit
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A circuit-driven, photoelectric isolation technology, applied in the field of electronic communication, can solve problems such as software driving difficulties, and achieve the effect of guaranteeing transmission, guaranteeing polling time, and guaranteeing real-time control.
Inactive Publication Date: 2012-08-01
DELTA GREENTECH CHINA CO LTD
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[0003] However, considering the problem of system anti-interference ability, the working power supply of 74HC165 comes from independent +5V, so the connection with the port of CPU (SH / LD, CLK and QH) must use optocoupler isolation signal; this brings the software driver of 74HC165 It must be difficult, the shifted pulse frequency is limited by the delay of the optocoupler
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Embodiment 1
[0030] In order to increase the switching value input capability of the CPU, an expansion circuit for parallel input and serial output is designed, so that only 3 GPIO ports of the CPU can be used to realize the input of 16 switching values. Such as figure 1 , using 2 pieces of 74HC165 parallel in serial expansion IC, using cascade connection to realize 16 digital input. SH / LD, CLK are the control signals of 74HC165, QH and SER are cascaded and serial input signals. Considering that the system needs to improve the anti-interference problem, the working power of 74HC165 comes from independent COMM+ and COMM- (+5V), so the SH / LD, CLK and QH connected to the CPU must use optocoupler to transmit signals, which gives the software driver of 74HC165 It brings certain difficulties, and the 74HC165 must be driven by an interrupt state machine to ensure the real-time control of the interface circuit.
[0031] see figure 2 , figure 2 It is the truth table of 74HC165, and the above ...
Embodiment 2
[0039] The invention discloses a method for driving a photoelectric isolation parallel-in-serial-out circuit, the method comprising:
[0040] Adopting at least one parallel-in-serial-out expansion IC chip, using a cascade connection method, to realize the input of N switching values; using an interrupt state machine to drive the IC chip;
[0041] The current state value of the IC chip is stored in the variable FSM, and in the initial state of the IC chip, the initial value of the FSM is 0;
[0042] Respond to a timer interrupt every set time length, in the interrupt, each state processes the operations required to be completed in this state and enters the next state in sequence, a total of 2*N states;
[0043] When entering the last state, store N switching value data in an N-bit variable Shift_R, each of which corresponds to an external switching value input, and then change the state variable FSM to the value corresponding to the initial state.
[0044] see image 3 , in t...
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Abstract
The invention discloses a driving method of a photoelectric isolation parallel-in-serial-out circuit. The method comprises the following steps of: adopting at least one parallel-in-serial-out extended IC (Integrated Circuit) chip and realizing the input of N switching values by using a cascade connection mode; driving the IC chip by adopting an interruption state machine; storing the current state value of the IC chip in a variable FSM (Finite State Machine), wherein the FSM has an initial value of 0 in an initial state of the IC chip; responding timer interception once at set time intervals,processing operations needing finishing in various states of the interception and sequentially entering the next state of the 2*N states in sum; storing the N switching value data in a N-bit variableShift_R when entering the final state, wherein each bit corresponds to one external switching value input, and then changing the FSM into a value corresponding to the initial state. The driving method of the photoelectric isolation parallel-in-serial-out circuit, which is proposed by the invention, drives the parallel-in-serial-out extended IC chip by adopting athe interception state machine so as to ensure the real-time control of an interface circuit.
Description
technical field [0001] The invention belongs to the technical field of electronic communication, and relates to a circuit driving method, in particular to a photoelectric isolation parallel-in and serial-out circuit driving method. Background technique [0002] see figure 1 , in order to increase the switching value input capability of the CPU, an expansion circuit for parallel input and serial output (such as parallel input and serial output of 74HC165 chips) is designed, so that a few GPIO ports can be used to realize multi-channel switch input, greatly Save GPIO resources. [0003] However, considering the problem of system anti-interference ability, the working power supply of 74HC165 comes from independent +5V, so the connection with the port of CPU (SH / LD, CLK and QH) must use optocoupler isolation signal; this brings the software driver of 74HC165 Certainly difficult, the shifted pulse frequency is limited by the delay of the optocoupler. Contents of the invention...
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