How to use 74hc573? Can 74hc573 be simulated?
This article mainly discusses how to use 74hc573 and whether 74hc573 can be simulated.
74HC573 latch usage
Pin 1 is output enable
Pin 11 is latch enable
D is input
Q is the output
H is high level, L is low
/OE is 1 pin LE is 11 pin
/OE is connected to low level to connect the output terminal of the internal data holder of the chip with the 8-bit output terminal of the chip.
The function of the LE terminal is to control the connection and disconnection of the 8-bit input and the input terminal of the internal data holder through the high and low level.
When LE = 0, the 8-bit data line of the P0 port is disconnected from the input of the 74HC573 internal data holder.
When LE = 1, the 8-bit data line of the P0 port is connected to the input of the 74HC573 internal data holder
Can 74hc573 be simulated? Answer: YesWith the development of single-chip technology, many peripheral circuits, such as functional modules such as AD, DA, and PWM, are integrated in the single-chip, and there is no need to expand as originally.
But like latch 74HC573, driver chip 74HC244 and 38 decoder, its function, principle and interface with controller are still the basis of embedded development and must be firmly grasped.
The thesis uses the latch 74HC573 to select the conversion channel of the analog-to-digital converter ADC0809 to achieve multiple conversion. The function of the latch 74HC573 is simulated in the Proteus environment to analyze the interface circuit design of the latch 74HC573.
In the proteus environment, add 74HC573 model, add debugging tools LOGICSTATE and LOGICPROBE, you can control the latch
The function is simulated. When OutputControl is the data output control terminal, it can realize the three-state output of the chip. When the level is high, the output terminal is in the high-impedance state. As shown in Figure 1, when the OE terminal is at the high level, no matter whether the LE state is high or Low, there is no signal at the output terminal, that is, high impedance state.
When OutputControl is low, the data is allowed to be output normally. If the LatchEnable terminal is high at the same time, the output and input follow.
The levels at both ends are the same, as shown in Figure 2, when the OutputControl terminal is low, if LatchEnable jumps from high to low at a certain moment,
Then the latch will latch the data state at the moment of transition in the output terminal, and the output terminal will not change with the input terminal, as shown in Figure 3.
The system connects the channel selection terminals A, B, and C of the ADC0809 analog-to-digital converter through the 74HC573, and sends a write command to the microcontroller to start conversion
When the ALE pin changes from high to low, the 74HC573 selects the channel and starts the analog-to-digital conversion. At the end of the conversion, a high level appears at the EOC terminal of the ADC0809 analog-to-digital converter. The 74HC04 reverse phase triggers the external interrupt of the microcontroller, and the interrupt subroutine Read the converted signal data to the corresponding
The storage area of ​​the main program is used for subsequent processing. The circuit principle is shown in Figure 4.
Below the schematic diagram are eight voltage signals, and use a voltmeter to display the current voltage value of the channel respectively to compare and verify with the LCD monitor value.
The LCD display data is provided by the P1 port. The RS, RW, and E terminals are controlled by P3.0, P3.1 and P3.2 respectively, and the P3.5 terminal is responsible for the lighting of the alarm lamp.
When the detected voltage value exceeds the limit,
P3.5 set low level to light up the red LED light to alarm.
Simulation results
The first line of the LCD display indicates the channel signal type, here is the voltage, which can be displayed differently according to the signal type, and the corresponding sampling data must be converted in units.
The actual value converted from voltage to physical quantity. At a certain moment, the CH1 voltage is 4.5V, the CH2 channel voltage is 3.00V, and the system detection voltage is 4.49V and 3.00V respectively. The simulation results are shown in Figure 6 and Figure 7, where the channel CH1 voltage value exceeds the set value. The upper limit of 4.3V, so the red LED on the left lights up and alarms.
in conclusion
In the Proteus environment, using AT89S52, analog-to-digital converter ADC0809, light-emitting diodes and liquid crystal displays, a set of monitoring system for production operation parameters is built to monitor eight production operation parameters, and the program is streamlined through modular programming. The maintainability of the code is improved , and the system is successfully simulated. The signal detection, LCD display and LED alarm functions are all normal, which has achieved the expected effect and has certain practical value.
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