Renesas H8S Series Hardware Manual page 358

Section 14 Serial Communication Interface (SCI)
Bit Bit Name Initial Value
1 CKE1 0
0 CKE0 0
Legend:
X: Don't care
Rev. 6.00 Mar 15, 2006 page 322 of 570
REJ09B0211-0600
R/W Description
R/W Clock Enable 0 and 1
R/W Selects the clock source and SCK pin function.
Asynchronous mode
00: Internal clock
SCK pin functions as I/O port
01: Internal clock
Outputs a clock of the same frequency as the bit
rate from the SCK pin.
1X:External clock
Inputs a clock with a frequency 16 times the bit
rate from the SCK pin.
Clocked synchronous mode
0X:Internal clock (SCK pin functions as clock output)
1X:External clock (SCK pin functions as clock input)