MAC7200 datasheet(452/976 Pages) FREESCALE

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PFLASH Application Usage

MAC7200 Microcontroller Family Reference Manual, Rev. 2

374

Freescale Semiconductor

18.7.7

Flash Programming Word Size

Due to the use of ECC on a 64-bit word in the Flash array with the 32-bit ARM core, locations in the flash

(both main array and Shadow Block) must be programmed in a special manner.

As an example, to program the 64-bit Double Word at address $0000 0000, you must perform the

following sequence of accesses in order:

1. 32-bit WRITE to address $0000 0000

2. 32-bit WRITE to address $0000 0004

Even if the data being stored is only 32-bits, you must execute the second 32-bit WRITE in order to

perform the actual write into the Flash array.

18.7.8

Read-while-Write (RWW)

Read-while-Write (RWW) refers to the ability to execute code from one partition while programming or

erasing another partition. For the definition of the partitions, please refer to Section 9.12, “Flash Main

Array Memory Map”. While doing a program/erase on one block in a partition, you cannot read from

another block within the partition, unless you do a suspend, and you cannot read from the block that is

being programmed/erased; however, you can do normal reads from blocks in other partitions.

18.7.9

Flash Security

The goal of total flash security is simple:

•

Prevent any data from a secured flash from being read out of the MAC72xx in any way, shape or

form.

•

Allow complete access to the Flash when it is unsecured

On the MAC72xx, the security is determined by the state of the System Censor word (Shadow Block

address offset $7de0).

On the MAC72xx, the System Censor word in a similar manner to the CFMSEC register in the MAC71xx

CFM Flash module, as follows:

18.7.9.1

Securing the device

In order to secure the device, you must perform the following steps:

1. Program bits [1:0] of the System Censor word (in the Shadow Block at address offset $7de0) to 00

or 11.

Table 18-13. System Censor Word Definition

shad_out[31:0]

Function

[31:30]

KEYEN: 10 = Backdoor access enabled (Currently not used)

[29:2]

Reserved for future use

[1:0]

SEC:

10 = unsecured, all other values = secured

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