HD64F3687GHV Datasheet, PDF (106/566 Pages) Renesas Technology Corp – Old Company Name in Catalogs and Other Documents

Section 5 Clock Pulse Generator
5.1 Features
• Choice of two clock sources
On-chip oscillator clock
Clock by an external oscillator output
• Choice of two types of RC oscillation frequency by the user software
16 MHz
20 MHz
• Frequency trimming
Since the initial frequency of the on-chip oscillator in the flash memory version is within the
range of two frequencies shown above, it is normally unnecessary to trim the frequency. It is,
however, still possible to adjust it by rewriting the trimming registers.
• Backup of the external oscillation halt
This system detects the external oscillator halt. If detected, the system clock source is
automatically switched to the on-chip oscillator clock.
• Interrupt can be requested to the CPU when the system clock is switched from the external
clock to the on-chip oscillator clock.
5.2 Register Descriptions
The CPG has the following registers.
• RC control register (RCCR)
• RC trimming data protect register (RCTRMDPR)
• RC trimming data register (RCTRMDR)
• Clock control/status register (CKCSR)
Rev. 3.00 Sep. 10, 2007 Page 72 of 528
REJ09B0216-0300