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====== lamaPLC: CJMCU-164; SN74HC164D 8-bit Shift Register Module ======
{{ :sensor:cjmcu-164.png?120|CJMCU-164; SN74HC164D 8-bit Shift Register Module}}
The CJMCU164 8-bit shift register board is based on the SN74HC164D IC. The SN74HC164D is an 8-bit serial-in parallel-out shift register.

**SN74HC164D**

These 8-bit shift registers have AND-gated serial inputs and an asynchronous clear (CLR). The serial inputs (A and B) can be controlled completely; a low level at either input prevents new data from entering and resets the first flip-flop to low at the next clock pulse (CLK). When an input is high, it allows the other to control the first flip-flop's state. Data at the serial inputs can be altered while CLK is high or low, provided the minimum setup time is met. Clocking happens on the low-to-high transition of CLK.

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{{ :sensor:cjmcu-164_5.png?400 |}}

**Technical data**
  * Supply voltage range, Vcc: –0.5 V .. 7 V
  * Input clamp current, IiK (Vi < 0 or Vi > Vcc): ±20 mA
  * Output clamp current, IoK (Vo < 0 or Vo > Vcc): ±20 mA
  * Continuous output current, Io (VO = 0 to Vcc): ±25 mA
  * Continuous current through Vcc or GND: ±50 mA

|{{ :sensor:cjmcu-164_2.png?400 |}}|{{ :sensor:cjmcu-164_3.png?400 |}}|

==== CJMCU-164 Pinout ====
{{ :sensor:cjmcu-164.png?200|CJMCU-164; SN74HC164D 8-bit Shift Register Module}}
^Pin Name^Type^Description|
^VCC|Power|Supply voltage (2V to 6V)|
^GND|Power|Ground|
^DSA (A)|Input|Serial Data Input A. AND-gated with DSB|
^DSB (B)|Input|Serial Data Input B. AND-gated with DSA|
^CP / CLK|Input|Clock Input. Shifts data on the low-to-high transition|
^MR / CLR|Input|Master Reset (Active LOW). Clears all outputs to LOW regardless of other inputs|
^Q0 – Q7|Output|8-bit Parallel Data Outputs|

**Pin Functions & Usage**

  * **Gated Serial Inputs (DSA/DSB):** These two pins are logically AND-gated. To use a single data line from your Arduino, connect one of these pins to 5V and send your data to the other, or simply tie both together.
  * **No Latch Pin:** Unlike the common 74HC595, the '164 lacks a storage/latch register. Data shifted into the register is immediately visible on the output pins (Q0–Q7) as it moves through the register.
  * **Daisy Chaining:** You can connect multiple CJMCU-164 modules by linking the Q7 output of the first module to a serial input (DSA or DSB) of the next

==== Arduino example code ====

**Arduino Pinout**

^CJMCU-164 Pin^Arduino Pin^Description|
^VCC|5V|Power Supply (2V to 6V)|
^GND|GND|Ground|
^DSA / DSB|Pin 2|Data Input (Connect one or both together)|
^CP (Clock)|Pin 3|Clock Input (Shifts on Low-to-High transition)|
^MR (Reset)|5V|Master Reset (Keep HIGH for normal operation)|

**Example Code**

This code uses the built-in //shiftOut()// function to send an 8-bit pattern to the register, which will light up LEDs or drive other parallel components.

<code c>
// Define pins connected to the CJMCU-164
#define DATA_PIN 2  // Connected to DSA/DSB
#define CLOCK_PIN 3 // Connected to CP

void setup() {
  // Set pins as outputs
  pinMode(DATA_PIN, OUTPUT);
  pinMode(CLOCK_PIN, OUTPUT);
}

void loop() {
  // Example 1: Send a binary pattern (B10101010)
  // This will turn on every other output pin (Q0-Q7)
  shiftOut(DATA_PIN, CLOCK_PIN, LSBFIRST, 0b10101010);
  delay(1000);

  // Example 2: "Walking" bit (Light one LED at a time)
  for (int i = 0; i < 8; i++) {
    byte pattern = (1 << i); 
    shiftOut(DATA_PIN, CLOCK_PIN, LSBFIRST, pattern);
    delay(200);
  }
}
</code>

**Key Technical Details**

  * **No Latch:** Because there is no latch (RCLK), the outputs will "flicker" briefly as new data bits are shifted through the register.
  * **Data Inputs:** The board typically has two data inputs (A and B) that are AND-gated. For standard use, tie them together or pull one HIGH and send data to the other.
  * **Shift Direction:** You can use LSBFIRST or MSBFIRST in the //shiftOut()// function, depending on which output pin (Q0 or Q7) you want to represent the first bit.

====== Source ======

https://docs.arduino.cc/tutorials/communication/guide-to-shift-out/ \\

===== Communication topics on lamaPLC =====
{{topic>communication}}

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{{tag>CJMCU-164 SN74HC164D 8-bit_Shift_Register SN74HC164D communication 7-segment CJMCU Arduino}}
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