PXD10RM Datasheet, PDF (168/1332 Pages) Freescale Semiconductor, Inc – PXD10 Microcontroller

If public access is not allowed but the flash is not secured, the received password is compared with the
value saved on NVPWD0 and NVPWD1 registers.
In both of previous cases, comparison is done by BAM application. If it goes wrong, BAM pushes MCU
into static mode.
In case of public access not allowed and flash secured, the password is written into SSCM.PWCMPH-L
registers.
After a fixed time waiting, comparison is done by hardware. Then BAM verifies again SSCM_STATUS’s
SEC flag:
• SEC = 0, flash is now unsecured and BAM continues its task
• SEC = 1, flash is still secured because password was wrong; BAM puts MCU to standby mode.
This fixed time depends on the external crystal oscillator frequency (FXOSC). With FXOSC of 12 MHz,
the fixed time is 350 ms.
SSCM.
STATUS.
PUB
comparison with
=1
0xFEEDFACE
CAFEBEEF
=0
SSCM.
STATUS.
=0
SEC
=1
Write received password to
SSCM.PWCMPH-L
comparison with
password saved on
NVPWD0-1
Wait
verify if Flash is
unsecured
Figure 6-5. Password Check Flow
6.5.4.6 Download start address, VLE bit and code size
The next 8 bytes received by the MCU contain a 32-bit Start Address, the VLE mode bit and a 31-bit code
Length as shown in Figure 6-6.
The VLE bit (Variable Length Instruction) is used to indicate for which instruction set the code has been
compiled. This device family supports only VLE = 1, the bit is used for backward compatibility.
6-10
PXD10 Microcontroller Reference Manual, Rev. 1
Preliminary—Subject to Change Without Notice
Freescale Semiconductor