AT697F_14 datasheet(48/176 Pages) ATMEL

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AT697F

7703E–AERO–08/11

The protected memory bank is partitioned as follows:

•

lower 80% of the memory bank available as program or data memory

•

upper 20% of the memory bank allocated to the EDAC checkbits (a maximum of 4

unusable bytes before the checkbit area)

Accessing the EDAC checkbits is performed as follows:

•

start address from the topmost byte in the same memory bank (no bank size

information needed)

addrcheckbits = addrbank-top - ((addrdata - addrbank-start) / 4)

•

checkbits bytes allocated downwards (address bits inversion technique used)

Figure 29. 8-bit EDAC-Protected Memory Organization

data1 byte0

data1 byte1

data1 byte2

data1 byte3

data2 byte0

data2 byte1

data2 byte2

data2 byte3

checksum2

checksum1

rre

spo

ing

eck

sum

0x00000007

0x00000006

0x00000005

0x00000004

0x00000003

0x00000002

0x00000001

0x00000000

0x0FFFFFFF

0x0FFFFFFE

memory top address

EDAC Testing

Operation of the EDAC can be bypassed for testing purpose and is controlled in a mem-

ory configuration register (MCFG3).

Figure 30. EDAC testing overview

Memory Configuration Reg.

MCFG3

CB[7:0]

EDAC

TCB

Write Test

When EDAC write bypass is enabled (MCFG3.wb = 1), the test checkbits (MCFG3.tcb)

replace the EDAC generated checkbits during a data store.

Read Test

When EDAC read diagnostic is enabled (MCFG3.rb = 1), the test checkbits

(MCFG3.tcb) are updated(1) with the read checkbits during a data load or an instruction

fetch.

Note:

1. The EDAC test routine shall be executed entirely from the instruction cache (when

activated) or from an area without EDAC activated and different from the one being

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