MAC7200 datasheet(477/976 Pages) FREESCALE

477 / 976 page

MAC7200 Microcontroller Family Reference Manual, Rev. 2

Freescale Semiconductor

399

Chapter 20

Boot Assist Module (BAM)

20.1

BAM Introduction

The Boot Assist Module (BAM) provides the JTAG Lockout Recovery functionality that was available in

hardware on the MAC71xx family of devices. It is essentially an AHB slave containing hard-code

instructions to perform the following sequence of events:

1. Unlock all Flash registers (PFCR2 register)

2. Enable the Flash for read/write (PFAPR register)

3. Configure the DACC/SACC registers

4. Enable LAS and MAS (LML register)

5. Enable HAS (HBL register)

6. Enable Shadow (SLL)

7. Enable all blocks for program/erase

8. Erase the main array

— Set the ERS bit

— Perform an interlock write

— Set the EHV bit

9. Wait until erase is done (DONE=1)

10. Check that the erase was successful (PEG=1)

11. Clear the EHV bit

12. Clear the ERS bit

13. Erase the shadow array

— Set the ERS bit

— Perform an interlock write

— Set the EHV bit

14. Wait until erase is done (DONE=1)

15. Check that the erase was successful (PEG=1)

16. Clear the EHV bit

17. Clear the ERS bit

18. Program the System Censor word in the Shadow Block

— Set the PGM bit

— Perform a program write (Write $80000002 to address SHADOW_BASE+$7de0)

MAC7200 Datasheet(PDF) 477 Page - Freescale Semiconductor, Inc