ARP Request w/ all 1 bit in ARP target hardware address

Hi,

I just noticed that one of my embedded devices is sending ARP request with all 1 bit in the target hardware address of the ARP packet. I think the protocol is using all 0 in the target hardware address. And the destination address is all 1 bit in Ethernet frame which is normal for ARP request.

Anybody has idea why the ARP request is different than other normal ones? Is that a special case?

Thanks.