Driving method of photoelectric isolation parallel-in-serial-out circuit

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 variable Shift_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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Problems solved by technology

[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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