Datasheet

Section 15 Serial Communication Interface (SCI, IrDA)
R01UH0309EJ0500 Rev. 5.00 Page 897 of 1408
Sep 24, 2012
H8S/2456, H8S/2456R, H8S/2454 Group
15.4.3 Clock
Either an internal clock generated by the on-chip baud rate generator or an external clock input at
the SCK pin can be selected as the SCI's serial clock, according to the setting of the C/A bit in
SMR and the CKE1 and CKE0 bits in SCR. When an external clock is input at the SCK pin, the
clock frequency should be 16 times the bit rate used.
When the SCI is operated on an internal clock, the clock can be output from the SCK pin. The
frequency of the clock output in this case is equal to the bit rate, and the phase is such that the
rising edge of the clock is in the middle of the transmit data, as shown in figure 15.4.
0
1 frame
SCK
TxD
D0 D1 D2 D3 D4 D5 D6 D7 0/1 1 1
Figure 15.4 Relation between Output Clock and Transfer Data Phase
(Asynchronous Mode)