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From: "Brian Adams" <brian.adams@a...>
Date: Wed, 25 Jun 2003 11:51:42 -0400
Subject: [openrisc] WB:RISC Clock Ratios

Hello All,

  I have a (hopefully) quick sanity check to ask. For the SOC we are
designing we want to have the ability to run WB:RISC clock ratios of 1:1
or 1:2.  To do this I would have to (?)

1) Define OR1200_CLKDIV_2_SUPPORTED
2) Drive clmode_i on or1200_top appropriately (we plan to use an
external switch or jumper)
3) Drive iwb_clk_i and dwb_clk_i with either the full or half rate WB
clock (depending on how we set #2)

  Also, are there restrictions on the 1:2 WB/RISC clock relationships?
ie. Must the WB clock must be EXACTLY 1/2 the RISC clock, and phase
aligned.  We plan to have both, but I was wondering if either was
absolutely necessary.

 I it appears that OR1200_CLKDIV_2_SUPPORTED, OR1200_CLKDIV_4_SUPPORTED
and clmode were added to make it easy to do just what I have proposed,
but I have been wrong before. =)
 
Thanks,
Brian

Follow up	Author
Re: [openrisc] WB:RISC Clock Ratios	Damjan Lampret