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SMTM32F4 ETH driver

Question asked by 56390 on Nov 18, 2013
Latest reply on Feb 5, 2014 by 56390
I am a beginner with STM32F4 and I am study the ETH driver procedure but I don't understand some instructions
For example:

  /* Clear MBC bits in the selected MAC address  high register */
  (*(__IO uint32_t *) (ETH_MAC_ADDR_HBASE + MacAddr)) &=(~(uint32_t)ETH_MACA1HR_MBC);
  /* Wait until the write operation will be taken into account :
   at least four TX_CLK/RX_CLK clock cycles */
  tmpreg = (*(__IO uint32_t *) (ETH_MAC_ADDR_HBASE + MacAddr));
  (*(__IO uint32_t *) (ETH_MAC_ADDR_HBASE + MacAddr)) = tmpreg;

I don't understand the read and write same register after delay 

Thanks in advance for help