Switch signal output interface circuit

Shown is the switching signal output interface circuit. The CPU only needs to execute an output instruction to write the logical digital signal into
the output latch IC Z (74LS273).
The latch control signal of the latch is output from the address line through the IC1
decoder and is connected to the WR signal. or get later. The output of the latch turns the light emitting diode LED on or off
via IC3 and IC
4. When the corresponding output bit Di is
"1", the light-emitting diode lights up. On the contrary,
when it is "07", the light-emitting diode goes out to indicate
the operating status of the computer control system. The system working status
often needs to be set to manual status "M", automatic status.
State "A", cascade (external given) state "C",
fault state "F", etc. System signal alarm states that
often need to be set include signal low alarm state
"AL" and signal high alarm state "AH". Its "F", "AH" and "AL" signals are output through an optically isolated power amplifier in order to drive
a higher-power switch actuator alarm (such as audible alarm, etc.). The output that is not connected to the LED can be used as a logic control output interface. .
    Optical isolation power amplifiers already have integrated circuits. The commonly used optical isolation power output device MOC series has two input levels (open collector
level and TTL level) interface circuit diagram , which can be used as an isolation power driver for the switching output interface. , in Figure 7-38,
a circuit with open collector level input should be used. If the driving capability cannot meet the requirements of the switch actuator, a larger power amplifier circuit can be added later.