SH7641 Datasheet, PDF (199/1036 Pages) Renesas Technology Corp – Renesas 32-Bit RISC Microcomputer SuperH™ RISC engine Family / SH7641 Series

Section 4 Clock Pulse Generator (CPG)
4.4 Register Descriptions
The CPG's control register is called the frequency control register (FRQCR). Refer the section 24,
List of Registers, for the addresses of the registers and the state of each register in each processor
state.
4.4.1 Frequency Control Register (FRQCR)
The frequency control register (FRQCR) is a 16-bit readable/writable register used to specify
whether a clock is output from the CKIO pin, the frequency multiplication ratio of PLL circuit 1,
and the frequency division ratio of the internal clock and the peripheral clock.
Only word access can be used on the FRQCR register.
This register is initialized (to H'1003) only in the case of a power-on reset. This register retains its
previous value after a manual reset or period in standby mode. The previous value is also retained
when an internal reset is triggered by an overflow of the WDT.
Initial
Bit
Bit Name Value R/W Description
15 to 13 
All 0
R
Reserved
These bits are always read as 0. The write value
should always be 0.
12
CKOEN
1
R/W Clock Output Enable
CKOEN specifies whether a clock is output from the
CKIO and CKIO2 pins, or whether the CKIO and
CKIO2 pins is placed in the level-fixed state during
release of the standby mode (until the state enters
STATUS1 = L and STATUS0 = L from an interrupt). If
CKOEN is cleared to 0, the CKIO and CKIO2 pins are
fixed at low during STATUS1 = L and STATUS0 = H.
Therefore, the malfunction of an external circuit
because of an unstable CKIO clock during release of
the standby mode can be prevented. In clock
operating mode 7, the CKIO pin functions as an input
regardless of this bit value.
0: The CKIO pin is fixed to the low level in the standby
mode and while the system is leaving standby
mode.
1: Clock is output from CKIO pin (placed in the high-
impedance state during periods in standby mode).
Rev. 4.00 Sep. 14, 2005 Page 149 of 982
REJ09B0023-0400