The serial data transmission unit 2, wherein said value read from {TAIL ~ the program} by {HEAD ~ 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 said value read from { TAIL ~ the program } by { HEAD ~ 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 OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH