Intel manual Redboot Intel IQ80321 DDR Memory Initialization Sequence

Intel® IQ80321 I/O Processor Evaluation Platform

Software Reference

5.4.6Redboot Intel® IQ80321 DDR Memory Initialization Sequence

In order to set the correct ECC bits, a DDR memory system (DIMM or discrete components) must be written to with a known value. This process requires 64-bit writes to the entire DDR memory intended for use. The following explains the sequence for memory initialization by Redboot on an IQ80321 board with an ECC DIMM. It also includes an example for the scrub (ECC initialization) code.

Initialization Sequence:

1.Disable interrupts. (Technically they are disabled at reset, but for soft reset this is included.

2.Init PBIU (Peripheral Bus Interface Unit) chip selects.

3.Enable I cache.

4.Move Flash to 0xF0000000.

5.Set TTB and Enable MMU.

6.Read DIM for memory parameters.

7.Set Memory Drive Strengths.

8.Set Memory Parameters.

9.Delay.

10.Turn DDRAM on.

11.Delay.

12.Enable Data Cache.

13.Enable BTB.

14.Flush all.

15.Clear ECC error logs.

16.Battery Test.

17.Enable ECC.

18.Scrub loop: Write zeros to all memory locations

mov	r8, r4	// save DRAM size
mov	r0, #-1
mov	r1, #-1
mov	r2, #-1
mov	r3, #-1
mov	r4, #-1
mov	r5, #-1
mov	r6, #-1
mov	r7, #-1
ldr	r11, = SDRAM_BASE
// scrub Loop
0:
stmia	r11!, {r0-r7}
subs	r12, r12, #32
bne	0

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