Eliminating RTC from MPC5200

Eliminating RTC from MPC5200

[Grant Likely]

I'm working on a design using the MPC5200.  The hardware engineer I'm
working has asked if he could omit the crystal for the RTC.  I've
searched through the Linux source (2.6.11) and it seems that the on
the lite5200 the RTC is being used to measure both the system clock
and the decrementer speed for the serial port.  It does not look like
the RTC is used otherwise.

Is this true?  Can I eliminate the need for the RTC If I modify
mpc52xx_calibrate_decr() in arch/ppc/syslib/mpc52xx_setup.c and
mpc52xx_ipbfreq() in arch/ppc/boot/simple/mpc52xx_tty.c?  I'm assuming
that I can hard code the system clock speeds for my specific hardware.

Thanks,
g.

Re: Eliminating RTC from MPC5200

[Daniel Ann]

On Apr 12, 2005 3:30 AM, Grant Likely <glikely@gmail.com> wrote:
> Is this true?  Can I eliminate the need for the RTC If I modify
> mpc52xx_calibrate_decr() in arch/ppc/syslib/mpc52xx_setup.c and
> mpc52xx_ipbfreq() in arch/ppc/boot/simple/mpc52xx_tty.c?  I'm assuming
> that I can hard code the system clock speeds for my specific hardware.

This kinda relates back to my previous post.
Tho I'm not using mpc52xx, my board doesnt have RTC as well. And I
simply blocked out all the time related functions except the
calibrate_decr. And hard coded the freq.

It works nicely.

BTW, I'm using mpc8245. You should be able to find my post dating back
no more than a week or two. Originally I had trouble working out the
freq, but its all solved thanks to Mark ^^

-- 
Daniel