HD64F2638F20J Datasheet, PDF (508/1512 Pages) Renesas Technology Corp – Renesas 16-Bit Single-Chip Microcomputer H8S Family/H8S/2600 Series

Section 13 Serial Communication Interface (SCI)
H8S/2639, H8S/2638, H8S/2636,
H8S/2630, H8S/2635 Group
Bits 1 and 0—Clock Enable 1 and 0 (CKE1, CKE0): These bits are used to select the SCI clock
source and enable or disable clock output from the SCK pin. The combination of the CKE1 and
CKE0 bits determines whether the SCK pin functions as an I/O port, the serial clock output pin, or
the serial clock input pin.
The setting of the CKE0 bit, however, is only valid for internal clock operation (CKE1 = 0) in
asynchronous mode. The CKE0 bit setting is invalid in clocked synchronous mode, and in the case
of external clock operation (CKE1 = 1). Note that the SCI’s operating mode must be decided using
SMR before setting the CKE1 and CKE0 bits.
For details of clock source selection, see table 13.9.
Bit 1 Bit 0
CKE1
0
CKE0
0
Description
Asynchronous mode
Internal clock/SCK pin functions as I/O port^*1
Clocked synchronous
mode
Internal clock/SCK pin functions as serial clock
output^*1
1
Asynchronous mode
Internal clock/SCK pin functions as clock output^*2
Clocked synchronous
mode
Internal clock/SCK pin functions as serial clock
output
1
0
Asynchronous mode
External clock/SCK pin functions as clock input^*3
Clocked synchronous
mode
External clock/SCK pin functions as serial clock
input
1
Asynchronous mode
External clock/SCK pin functions as clock input^*3
Clocked synchronous
mode
External clock/SCK pin functions as serial clock
input
Notes: 1. Initial value
2. Outputs a clock of the same frequency as the bit rate.
3. Inputs a clock with a frequency 16 times the bit rate.
Page 458 of 1458
REJ09B0103-0800 Rev. 8.00
May 28, 2010