[Open-graphics] How to initialize memory

[Timothy Normand Miller]

I had to add a clock-enable control to reg 3 of the arbiter.  Now it's:
[10:0] refresh delay
[11] refresh enable
[12] clock enable


Here's the startup sequence:

- First, cke is already reset to zero
- Set cke to 1, refresh enable to zero
- Precharge command
- Load Extended MR with 15'b01_00000000000_0_0
- Load MR with 15'b00_000010_011_0_001 (I think - must reset the DLL)
- Precharge command
- Load the refresh counter, with cke and refresh enable set to 1
- Wait 10 microseconds
- Load MR with 15'b00_000000_011_0_001 (I think)


-- 
Timothy Normand Miller
http://www.cse.ohio-state.edu/~millerti
Open Graphics Project