Ive been doing a bit more digging and it seems the SH7709 processor in the J680 may be capable of running at 200MHz
The part comes in various speed ratings including 100/133/167/200Mhz
The maximum operating frequency of the CPU core, MMU and cache is 200MHz.
The maximum operating frequency of the external bus interface is 66.67MHz.
The DMA controller uses the bus state controller.
The maximum operating frequency of these on-chip peripheral functions is 33.34MHz.
The processor clock can be set programmatically as a multiple of the xtal freq of 16.67MHz. The peripheral and bus clocks can also be set independently.
There is a good resource here
Renesas E learning Super-H
There is an included code sample for changing the clock freq
SH7709S example code
/* Clock Pulse Generater sample program Mode = 2 PLL2 FIXED=*4
X'tal = 16.7MHz
PLL1 = *4
FRQCR H'0102(startup) I:B: P=4:4:1 66.7:66.7:16.7 MHz
*/
#include "iodefine.h"
void pll4(void) ;
void pll3(void) ;
void idiv3(void) ;
void idiv1(void) ;
void pll4(void)
{
CPG.WTCNT = 0x5a00 ; // Watch dog timer counter = 0
CPG.WTCSR = 0xa502 ; // 1/16Pclk : 122us ( >100us)
CPG.FRQCR.WORD = 0x0112 ; //bin 000100010010 PLL1 is *2 (I:B: P=8:4:2)
}
void pll3(void)
{
CPG.WTCNT = 0x5a00 ; // Watch dog timer counter = 0
CPG.WTCSR = 0xa502 ; // 1/16Pclk : 122us ( >100us )
CPG.FRQCR.WORD = 0xa101 ; // bin 1010000100000001 PLL1 is *3 (I:B: P=12:4:2)
} // change only CPU clock divider1
void idiv3(void)
{
CPG.FRQCR.WORD = 0xe101 ; // bin 1110000100000001 IFC=1/3 (I:B: P=4:4:2)
}
void idiv1(void)
{
CPG.FRQCR.WORD = 0xa101 ; //bin 1010000100000001 IFC=1/1 (I:B: P=12:4:2)
}
Here are the bit mappings for the multiplier/ divider settings
Bit 15=1 Bit5=0 Bit4=0. STC1=*3 PLL1=*3
Bit 15=0 Bit5=0 Bit4=1 STC1=*2 PLL1=*2
Bit14=1 Bit3=0 Bit2=0 IFC=1/3
Bit14=0 Bit3=0 Bit2=0 IFC=1
Bit13=1 Bit1=0 Bit0=1 PFC=1/6
And more complete application note for changing clock freq for an earlier H7670 here:
change clock freq H7670
Once I have enough postings to be able to download, I will install Embedded Visual Tools 3.0
(eVT 3.0
) and try to make a simple app to target the clock multipliers of the SH7709 and therefore overclock to 167 or 200 MHz
Edited by Stevetuc 2022-01-07 1:31 PM