uSD

Secure Digital  ( SD)  is a non-volatile memory card format developed by the SD Card Association (SDA) for use in portable devices.

The newer families of SD card improve card speed by increasing the bus rate (the frequency of the clock signal that strobes information into and out of the card).
Whatever the bus rate, the card can signal to the host that it is "busy" until a read or a write operation is complete. Compliance with a higher speed rating is a
guarantee that the card limits its use of the "busy" indication. Size: 15 x 11 x 1 mm

 
IMPORTANT:  Make sure that your Ethernet PLC is powered (12-24Vdc).

To know more about the microSD...

General Features

The maximum capacity is  4 GB . If a higher capacity is used, it will work correctly but only the first 4GB will work. Allowed file system architectures:  FAT32  &  

FAT16. 

The micro SD uses the SPI communication to interact with the Arduino Mega. The SPI protocol is always enabled, as there are no switches that configure it.
However there is a switch that must be placed to ON mode in order to communicate with the uSD:

D53(SD) : If this Switch is  OFF , it  enables the Chip Select of the microSD socket  and  disables Q2.0 . If this switch is ON, it enables the Q2.0 output, so  if
the switch is in ON mode the microSD can’t be used . 

Using the  boards  of  Industrial Shields , there is a  library  that simplifies the uSD implementation

called  SD . It is the same as the Arduino library, with the only modification of using the pin 53 to select the Chip Select of the uSD chip.

Connections

Software

Using the  boards  of  Industrial Shields , there is a library that  simplifies the uSD implementation called SD . It is the same as the Arduino library, with the only modification of using the  pin 53 to select the ChipSelect of the uSD chip .

So, firstable it is necessary to include the SD.h library provided in our boards: 

#include <SPI.h>
#include <SD.h>
Sd2Card card;
SdVolume volume;

///////////////////////////////////////////////////////////////////////////////////////////////
void setup() {
  Serial.begin(9600L);
  Serial.println("M-Duino PLUS test started");

// we'll use the initialization code from the utility libraries
// since we're just testing if the card is working!
  if (!card.init(SPI_HALF_SPEED, 53)) {
    Serial.println("initialization failed. Things to check:");
    Serial.println("* is a card inserted?");
    Serial.println("* is your wiring correct?");
    Serial.println("* did you change the chipSelect pin to match your shield or module?");
    return;
  } else {
    Serial.println("Wiring is correct and a card is present.");
  }

  // print the type of card
  Serial.print("\nCard type: ");
  switch (card.type()) {
    case SD_CARD_TYPE_SD1:
      Serial.println("SD1");
      break;
    case SD_CARD_TYPE_SD2:
      Serial.println("SD2");
      break;
    case SD_CARD_TYPE_SDHC:
      Serial.println("SDHC");
      break;
    default:
      Serial.println("Unknown");
  }

  // Now we will try to open the 'volume'/'partition' - it should be FAT16 or FAT32
  if (!volume.init(card)) {
    Serial.println("Could not find FAT16/FAT32 partition.\nMake sure you've formatted the card");
  } else {
    // print the type and size of the first FAT-type volume
    uint32_t volumesize;
    Serial.print("\nVolume type is FAT");
    Serial.println(volume.fatType(), DEC);
    Serial.println();
  
    volumesize = volume.blocksPerCluster();    // clusters are collections of blocks
    volumesize *= volume.clusterCount();       // we'll have a lot of clusters
    volumesize *= 512;                            // SD card blocks are always 512 bytes
    Serial.print("Volume size (bytes): ");
    Serial.println(volumesize);
    Serial.print("Volume size (Kbytes): ");
    volumesize /= 1024;
    Serial.println(volumesize);
    Serial.print("Volume size (Mbytes): ");
    volumesize /= 1024;
    Serial.println(volumesize);
  }
}

///////////////////////////////////////////////////////////////////////////////////////////////
void loop() {}

For more detailed information about SD class information check the  SD  library repository. 

5Vdc Signals

 These pins can be programmed according to Arduino features such as I/Os operating at 5V or any additional features present in the pins. 

    I2C Pins – SDA/SCL:

The I2C protocol is meant to work in a pull-up configuration. In this case it reads 5V when nothing is connected.

    Serial 0 – RX0/TX0:

The Serial0 protocol can work also as a 5V pin. If using these pins, the USB communication cannot be working at the same time.

    Serial 1 – RX1/TX1:

The Serial1 protocol can work also as a 5V pin. Always enabled.

    SPI – MISO/MOSI/SCK:

These pins can only work as a 5V pins if the Ethernet protocol is not going to be used. As the Ethernet protocol uses the SPI to communicate with the
Arduino board, both behaviors cannot happen at the same time as the Ethernet would not work.

    Pin2/Pin3:

These pins are only referred to the inputs I0.5/I0.6. If the switch configuration is in OFF position the pins Pin 2/Pin 3 will be available.