The serial data transmission unit 2, wherein {HEAD ~ said value} read from the program by {TAIL ~ said CPU} is determined considering a longest one of data holding intervals of said plurality of external slaves 
The serial data transmission unit 2 , wherein { HEAD ~ said value } read from the program by { TAIL ~ said CPU } is determined considering a longest one of data holding intervals of said plurality of external slaves
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH