LPC Microcontrollers中的主题 Re: The EMC clock limitation

The EMC clock limitation

lpcware — Wed, 15 Jun 2016 18:06:12 GMT

Content originally posted in LPCWare by Mori_64 on Mon Jan 05 08:06:49 MST 2015
Hello

As i see in lpc1788 user manual :

Quote:
Clock: The EMC clock can be the same as the CPU clock (the default), or half that.
The lower rate is intended to be used primarily when the CPU is running faster than
the external bus can support. Clock selection for the EMC is described in

but is there any limitation ?

for example can i use sd_ram in 120 Mhz ?

Best Regards

Re: The EMC clock limitation

lpcware — Wed, 15 Jun 2016 18:06:13 GMT

Content originally posted in LPCWare by mc on Mon Jan 05 09:42:29 MST 2015
Hi Mori_64,
Maximum data transfer speed with SDRAM is also limited by the speed of the IO. So, either you can run device at core frequency of 80MHz and SDRAM clock at 80MHz or you can run core at 120MHz and SDRAM at 60MHz.

Re: The EMC clock limitation

lpcware — Wed, 15 Jun 2016 18:06:14 GMT

Content originally posted in LPCWare by Mori_64 on Tue Jan 06 06:54:55 MST 2015
Hi mc

Thanks for your replay .
I tested my sd_ram with 120Mhz and it works fine !

Re: The EMC clock limitation

lpcware — Wed, 15 Jun 2016 18:06:14 GMT

Content originally posted in LPCWare by MikeSimmonds on Tue Jan 06 16:48:04 MST 2015
It may be working fine at the temperatures on the testing bench and with the voltage and power
that were used in your (limited? simple?) tests, but you are are running at 150% over the rated guaranteed specification!
On long term running or when different operating characterists apply, you won't have any come-back.

Any form of over-clocking is entirely at your own risk.

This may not concern you for hobby projects, but such practice is totaly unacceptable in any commercial enterprises.

As the saying goes ... you have been warned.

EDIT: you need to read the data sheet for the part for limits etc. not the generic user manual for the family.

Regards, Mike

Re: The EMC clock limitation

lpcware — Wed, 15 Jun 2016 18:06:15 GMT

Content originally posted in LPCWare by bavarian on Wed Jan 07 08:26:11 MST 2015
Mike is right. Even if the memory interface in this chip is quite robust with regards to overclocking, running it on 120MHz is at your own risk.
At least you need to run a stress test over the possible voltage and temperature range. Lower voltage and higher temperature is the worst case for this test.

Regards,
NXP Support Team.