PM0222 datasheet(18/33 Pages) STMICROELECTRONICS

18 / 33 page

Flash controller

PM0222

18/33

DocID025476 Rev 1

MASSWRITE sequence:

–

Write the unique value to program in all the main Flash memory in the Flash

Controller DATA register.

–

Write the MASSWRITE command (0x44) in the Flash Controller COMMAND

–

Wait for the CMDSTART flag in the IRQSTAT register (polling mode or interrupt

mode) indicating that the command has been taken into account and is under

execution.

–

Clear the CMDSTART flag by writing CMDSTART to ‘1’ in the Flash Controller

IRQSTAT register.

–

Wait for the CMDDONE flag in the IRQSTAT register (polling mode or interrupt

mode), indicating that the command is completed.

–

Clear the CMDDONE flag by writing CMDDONE to ‘1’ in the Flash Controller

IRQSTAT register.

6.3

Locked / Unlocked feature

Flash memory is protected from a read when the device is in debug mode. This means as

soon as Cortex-M0 is halted, any access to Flash memory will return a fixed 0x0 value and

generate an AHB error if the debugger tries to read it.

Note that RAM bank0 and RAM bank1 memories are also concerned by this lock protection.

To unlock the Flash and RAM memories and render them readable through JTAG, it is

necessary to fill UNLOCKM and UNLOCKL with the 64-bit unlock code. This code

corresponds to the two last words inside the main Flash so the condition to unlock them is:



UNLOCKM[31:0] = value at address 0x1001_FFF8 (if REMAP = ‘0’ else 0x1002_FFF8)



UNLOCKL[31:0] = value at address 0x1001_FFFC (if REMAP = ‘0’ else 0x1002_FFFC)

The 64-bit code in Flash (the two last words inside the memory) is latched automatically

before the Cortex-M0 reset is released.

The default value in the UNLOCKM and UNLOCKL registers is 0xFFFF_FFFF

corresponding to unwritten or erased Flash. As soon as the customer modifies the two last

words inside Flash memory, he will need to program the UNLOCKM and UNLOCKL

registers to be able to access Flash and RAM in debug mode.

This UNLOCKM / UNLOCKL register programming can be done through JTAG at the

beginning of the debugging session.

Caution:

The UNLOCKM and UNLOCKL registers of the Flash Controller can be written only once

after reset. Any further write will not be taken into account.

Note:

This lock protection has no impact for Flash / RAM read by Cortex-M0 in a non-test mode. It

concerns only debug mode.

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