If you're going to be accessing the hardware registers directly, why
not just read the CPU frequency from them? This is how I do it for
the VZ -- the SZ may be different (if that's what the NR70 uses).
int32 EmRegsVz::GetSystemClockFrequency (void)
{
uint16 pllControl = READ_REGISTER (pllControl);
uint16 pllFreqSel = READ_REGISTER (pllFreqSel);
// Convert the 32.768KHz clock (CLK32) into the PLLCLK frequency.
uint16 PC = (pllFreqSel & 0x00FF);
uint16 QC = (pllFreqSel & 0x0F00) >> 8;
uint32 result = 32768L * 2 * (14 * (PC + 1) + QC + 1);
// Divide by the first prescaler, if needed.
if ((pllControl & hwrVZ328PLLControlPreSc1Div2) != 0)
{
result /= 2;
}
// Divide by the second prescaler, if needed.
if ((pllControl & hwrVZ328PLLControlPreSc2Div2) != 0)
{
result /= 2;
}
// Divide by the system clock scaler, if needed.
switch (pllControl & 0x0F00)
{
case hwrVZ328PLLControlSysDMADiv2:
result /= 2;
break;
case hwrVZ328PLLControlSysDMADiv4:
result /= 4;
break;
case hwrVZ328PLLControlSysDMADiv8:
result /= 8;
break;
case hwrVZ328PLLControlSysDMADiv16:
result /= 16;
break;
}
return result;
}
-- Keith
At 11:11 AM -0700 7/20/02, Robert Hildinger wrote:
>I've created the code below to calculate the CPU speed of a Sony
>Clie NR70 in MHz. The code works by calculating the time it takes to
>execute a block of 250 NOP instructions, which according to Motorola
>documentation takes 4 cycles to execute. 250 NOPs therefore equate
>to 1000 CPU cycles. The clock frequency is then easy to compute as a
>1000 cycles divided by the time take to execute in seconds. Easy,
>huh?
>
>Well, here's the problem... This code returns a value of 42-43 MHz
>every time, which is great except that the NR70's processor is
>supposed to run at 66 Mhz, and I'm at a loss as to figure out why
>there is such a discrepancy. I believe this calculation to be
>accurate, but the difference in results is undeniable. I thought
>that the problem might lie in interrupt procesing during my timing
>block, but the block is only a 1000 cycles long, but I can't see
>interrupts coming in consistently during such a short duration...
>
>Any thoughts????
>
>Thanks!
>-Robert Hildinger
>
>#define TCN1 0xfffff608; // Address of hardware TIMER 1 on Sony
> // NR70 (DragonBall Super VZ- runs at
> // 5526869 Hz
>#define IMR 0xfffff304; // Address of NR70 Interrupt Mask Reg.
>
>static void RunSpeedTest(void)
>{
> ...
> time = (volatile UInt16 *)TCN1;
> imr = (volatile UInt32 *)IMR;
> ...
>}
--
For information on using the Palm Developer Forums, or to unsubscribe, please see
http://www.palmos.com/dev/support/forums/
