EMC Clock

Discussion created by lpcware Employee on Jun 15, 2016
Latest reply on Jun 15, 2016 by lpcware
Content originally posted in LPCWare by Marc Crandall on Mon Aug 15 14:38:52 MST 2011

I'm trying to confirm the setting of the LPC1788 EMC Clock.

Basically I am seeing conflicting information in the tools and I'm not 100% sure about the wording of the user manual.

The attached image is the best place to begin my question.

As you see in this image (generated from Keil uVision 4.20) the EMC clock is listed at 39MHz.  The issue is that the EMCClock variable in "system_LPC177x_8x" is actually 78MHz.

The datasheet says that the EMC clock is either the CPU clock or the CPU clock / 2.

However if you look at the diagram in the user manual (Fig 7. Clock generation for the LPC178x/177x) it looks to me that the EMC clock is either sysclk or pll_clk optionally divided by 2.

So I hope this is somewhat clear.  Either the diagram is incorrect, the system_LPC177x_8x.c file is incorrect and/or the wording in the user manual is incorrect.

Can someone clarify this?