#include <TinyWireS.h> //You need this library to upload the sketch on your slave board

void setup()
{
TinyWireS.begin(8); //I2C communication
TinyWireS.onRequest(test);
}

void loop()
{
TinyWireS_stop_check();
}

void test () //Master calls the slave and the latter one send data
{
TinyWireS.send(0);
}