Intel IQ80333 - Manual (Page 50)

50 Customer Reference Board Manual
Intel® IQ80333 I/O Processor
Software Reference
4.3.4 RedBoot Intel
®
80332 I/O Processor 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 80333 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 Parameters.
8. Delay.
9. Turn DDRAM on.
10. Delay.
11. Enable Data Cache.
12. Enable BTB.
13. Flush all.
14. Clear ECC error logs.
15. Battery Test.
16. Enable ECC.
17. 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