SH7055S Datasheet, PDF (507/1002 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperH RISC engine Family/SH7000 Series

• Bits 1 and 0—Clock Enable 1 and 0 (CKE1, CKE0): These bits select the SCI clock source
and enable or disable clock output from the SCK pin. Depending on the combination of CKE1
and CKE0, the SCK pin can be used for serial clock output, or serial clock input. Select the
SCK pin function by using the pin function controller (PFC).
The CKE0 setting is valid only in asynchronous mode, and only when the SCI is internally
clocked (CKE1 = 0). The CKE0 setting is ignored in synchronous mode, or when an external
clock source is selected (CKE1 = 1). For further details on selection of the SCI clock source,
see table 15.9 in section 15.3, Operation.
Bit 1: Bit 0:
CKE1 CKE0 Description*¹
0
0
Asynchronous mode
Internal clock, SCK pin used for input pin (input signal
is ignored) or output pin (output level is undefined)*²
Synchronous mode
0
1
Asynchronous mode
Internal clock, SCK pin used for synchronous clock
output^*2
Internal clock, SCK pin used for clock output*³
Synchronous mode
1
0
Asynchronous mode
Internal clock, SCK pin used for synchronous clock
output
External clock, SCK pin used for clock input*⁴
Synchronous mode
External clock, SCK pin used for synchronous clock
input
1
1
Asynchronous mode
External clock, SCK pin used for clock input*⁴
Synchronous mode
External clock, SCK pin used for synchronous clock
input
Notes: *1 The SCK pin is multiplexed with other functions. Use the pin function controller (PFC) to
select the SCK function for this pin, as well as the I/O direction.
*2 Initial value.
*3 The output clock frequency is the same as the bit rate.
*4 The input clock frequency is 16 times the bit rate.
Rev.2.0, 07/03, page 469 of 960