MAC7200 datasheet(479/976 Pages) FREESCALE

479 / 976 page

BAM External Pins

MAC7200 Microcontroller Family Reference Manual, Rev. 2

Freescale Semiconductor

401

From a user/tool perspective, the sequence of events looks like the following:

1. If the device is powered off, perform a correct power on sequence first

2. Assert the external RESET of the device

3. While the RESET is asserted, write bit 9 of the SC4 register using the JTAG interface

4. Release the RESET

5. There is no need to clear bit 9 of the SC4 register, as it is self-clearing

6. Continuously poll the SC4 register (READ) until bit 8 (Lockout Recovery Complete) is set.

7. If bit 19 is set (1), it means that the system is secured, and the Lockout Recovery process must have

failed. If bit 19 is cleared (0), which is the expected result, then the system is unsecured.

8. Note that it is not necessary to write the Security Word in the system after performing the JTAG

Lockout Recovery, as this is done automatically during the procedure.

9. Once the device is unsecured, reset the device by asserting the RESET pin. You may reset into any

functional mode.

20.4

BAM External Pins

There are no BAM signals that drive or are driven from MCU pins.

20.5

BAM Bus Aborts

The BAM will signal a bus abort under any of the following conditions:

•

Access was not in Supervisor Mode

•

Access was 8 or 16 bits

•

Access was a WRITE

•

Access was a burst

Because the BAM resides as a slave on the crossbar switch, all bus aborts from the BAM will cause either

a Prefetch or Data Abort in the ARM7 core.

20.6

BAM Differences from MAC71xx

•

This is a new block, that was not present on the MAC71xx family

20.7

BAM Application Usage

Although the BAM is intended primarily for JTAG Lockout Recovery, the code contained in it is

completely visible to the application code. If the application code wants to perform a Lockout Recovery,

it may simply jump to address $A000 0000. However, the BAM code always end in an endless loop, which

can only be exited by resetting the device.

MAC7200 Datasheet(PDF) 479 Page - Freescale Semiconductor, Inc

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