is a string in and out with latch function shift register, its use is very simple, in normal use SCLR is high voltageFlat, G is low.
Usually I set ST_CP to a low level, and when the shift is over, a positive pulse (5V, more than a few tens of nanoseconds) is generated at the ST_CP end. I usually choose the microsecond level) to update the display data. /OE (pin 13) : Output prohibited at high voltage (high resistance).
Updates the display data. (13 pin) : Output forbidden at high voltage (high resistance state). The main advantage of 74595 is that it has a data storage register, and the data at the output end can remain unchanged during the shift process. This is useful when the serial speed is slowThe LED display device has no flicker sense.
should be 74HC595 output Max plus or minus 35 mA. The chip output current is 74HC595 as the center, 74HC output low voltage, can be injected into the chip current, at this time the current is positive 35Ma. At high voltages, current flows out of the chip, and the current is negative, with a maximum of negative 35 mA.
1, and when OE is high potential, that is, when the output is off, parallelThe output is maintained at high impedance.
2. Parallel expansion method The 74HC244 chip with three-state buffer and 74HC377 chip with output latch are used for parallel expansion of P0 port, which can realize more I/O ports. Among them, 74HC244 chip can realize the input and output control of P0 port, and 74HC377 chip can realize the output control and latch control of P0 port.
3, HC240 circuit 1Y2 output high level, relay release, contact disconnected, no signal output; When S1 is released, 1Y2 outputs a low level, followedid=' How to lock the latch of the LED light of the MCU? '> How to lock the latch of the LED light of the MCU?
1, in accordance with the procedures supplemented by the main building, it is necessary to connect two chips 73LS373, which is the latch.
2, this article will introduce the working principle of leds, diodes and latches to help readers better understand these components. The working principle of LED LED positive terminal high potential (Vcc), negative terminal P1, P1=0 that is, P1 is low potential at this time, LED has current flow so light.
3, with 51 MCU control 32 led lights, but not all with 32 IO pins, but also to achieve many ways of light off, which is easy to achieve.
4, prepare materials: You need to prepare the following materials: microcontroller (such as Arduino, STM32, etc.) LED lamp resistance (for current limiting, to prevent LED overcurrent damage) Connection cable Connection circuit: Connect the LED lamp to the microcontroller.
5, ALE (Address Lock Enable) function is to access the external memory, P0 port as an address/data multiplexingPort, ALE signal is used to latch low 8-bit addresses.
6, the latch is not necessary, may be the designer of the original drawing to consider their own programming habits and added. The low level of 51 MCU can definitely drive the LED directly (requiring a current-limiting resistor in series). The high level can be driven depending on the situation.
1, there are two types of data sent by the main module to the bus: oneIndicates broadcast data whose destination address is set to 0. The other is non-broadcast data that contains a specific destination address.
2, select the communication module to complete the transmission 1: rf905 is used for data transmission, and the two microcontrollers send data to 905 through the serial port, and then send it out through 905.
3, first of all, the microcontroller and microcomputer communication electrical standards to be consistent, the microcomputer serial port is generally RS232 electrical standards, so to add a level conversion chip, mostly with MAX232, the general microcontroller experiment board are provided with such a standard serial port.
1, Draw a simulation diagram in proteus, placed capacitors and resistors have parameters, double-click the parameters can be changed. That 5V is the power terminal, in the left toolbar terminal, see the picture below. Open the relevant window in proteus, and you need to select POWER in the position shown. If there is no problem in the next step, click and place according to the actual situation.
2,First, open proteus software on the computer, as shown in the figure. After entering the software interface, click the Terminal Mode tool icon. Then select "POWER" from the options that appear on the right and place it in the software editing area.
3. Click the icon indicated by the arrow in the picture below. You need to click the "P" button in the jump-off interface. You can see the numbers in the interface, enter "AT89C51", there will be a variety of 51 single-chip special aircraft. Next is a series of numbers, double click with the mouse.
4. Click the icon indicated by the arrow in the picture below. Click "P"Word button. Enter "AT89C51" and a variety of 51 single-chip special planes will appear. Double click with the mouse. Then the shortcut window will appear the selected microcontroller, select it and place it in the editing area. The microcontroller displays the grounding and power pins.
data end: Q0--Q7: eight-bit parallel output end, can directly control the eight segments of the nixie tube. Q7: cascaded output terminal. Take it to the DS end of the 595. DS: serial dataInput, if cascaded, connect to one level Q7.
In summary, the Arduino microcontroller should give two char data to the expansion board of the digital tube, data1 is the number displayed by the digital tube, and data2 is the position information of which digital tube is lit. After two bytes of data are sent in serial, the RCLK interface outputs a rising edge signal, and all the data is transferred from the register to the latch.
Since we want to use 74hc595, we must write a 595 driver in order to simplify the following operation. Data side of
:QA--QH: eight-bit parallel output terminal, which can directly control 8 segments of the nixie tube. QH ': Cascade output. I'll take it to the SI end of the 595. SI: serial data input terminal. 74595 control terminal description: /SRCLR (pin 10) : low normal time will clear the shift register data to zero.