AN4035 datasheet(35/42 Pages) STMICROELECTRONICS

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AN4035

System initialization

Doc ID 022669 Rev 2

35/41

System initialization

For Flash programming, there is some system initialization that needs to be performed by

the external tool.

The initialization to perform is the SRAM initialization.

5.1

Internal SRAM initialization

The SPC56x family of devices all contain internal SRAM that must be initialized after power-

on-reset by 64-bit writes to the entire memory. This is necessary to initialize the error-

correcting code (ECC) logic.

The easiest way to do this with an external tool is to single step over a number of stmw

(store multiple words) instructions with r0 as the rS field, the address to begin the writes in

WBBRlow, and CTL[FFRA] set. This causes all 32 GPRs to be written to memory beginning

at the address in WBBRlow using 64-bit writes. For example, the starting physical address of

the internal SRAM is 0x40000000. Stepping over stmw r0, 0(X) with the 0x40000000 in

WBBRlow causes all 32 GPRs to be written to memory starting at address 0x40000000

using 64-bit writes. Then 0x80 should be added to the address, written to WBBRlow and

stmw executed again. This should be done [size of internal SRAM] / [0x80] times to initialize

the entire internal SRAM.

5.2

Setting up the memory management unit

The memory management unit (MMU) on the SPC56x devices, that include this hardware

implementation (for example SPC560B devices don’t have this hardware implementation),

provides memory translation from effective to real addresses. For the purpose of Flash

programming, it is easiest to setup the MMU such that the effective addresses are the same

as the real addresses. For the CPU to access a memory mapped region, an MMU entry for

that memory space must be configured. The external tool has the capability to setup MMU

entries by writing the appropriate SPRs and single stepping over the tlbwe instruction.

For Flash programming, the external tool should set up at least four MMU entries. The steps

required to setup an MMU entry are:

Setup MAS0 (SPR 624).

Setup MAS1 (SPR 625).

Setup MAS2 (SPR 626).

Setup MAS3 (SPR 627).

Execute tlbwe (0x7C0007A4).

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