
UM10800
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© NXP Semiconductors N.V. 2016. All rights reserved.
User manual
Rev. 1.2 — 5 October 2016
366 of 487
NXP Semiconductors
UM10800
Chapter 24: LPC82x Flash controller
generation is complete. Code outside of the flash (e.g. internal RAM) can be executed
during signature generation. This can include interrupt services, if the interrupt vector
table is re-mapped to memory other than the flash memory. The code that initiates
signature generation should also be placed outside of the flash memory.
24.5.1.1 Signature generation address and control registers
These registers control automatic signature generation. A signature can be generated for
any part of the flash memory contents. The address range to be used for generation is
defined by writing the start address to the signature start address register (FMSSTART)
and the stop address to the signature stop address register (FMSSTOP. The start and
stop addresses must be aligned to 32-bit boundaries.
Signature generation is started by setting the STRTBIST bit in the FMSSTOP register.
Setting the STRTBIST bit is typically combined with the signature stop address in a single
write.
show the bit assignments in the FMSSTART and FMSSTOP
registers respectively.
24.5.1.2 Signature generation
A signature can be generated for any part of the flash contents. The address range to be
used for signature generation is defined by writing the start address to the FMSSTART
register, and the stop address to the FMSSTOP register.
The signature generation is started by writing a 1 to the SIG_START bit in the FMSSTOP
register. Starting the signature generation is typically combined with defining the stop
address, which is done in the STOP bits of the same register.
The time that the signature generation takes is proportional to the address range for which
the signature is generated. Reading of the flash memory for signature generation uses a
self-timed read mechanism and does not depend on any configurable timing settings for
the flash. A safe estimation for the duration of the signature generation is:
Duration = int((60 / tcy) + 3) x (FMSSTOP - FM 1)
When signature generation is triggered via software, the duration is in AHB clock cycles,
and tcy is the time in ns for one AHB clock.
After signature generation, a 32-bit signature can be read from the FMSW0 register. The
32-bit signature reflects the corrected data read from the flash and the flash parity bits and
check bit values.
24.5.1.3 Content verification
The signature as it is read from the FMSW0 register must be equal to the reference
signature. The following pseudo-code shows the algorithm to derive the reference
signature:
sign = 0
FOR address = FMSSTART.START to FMSSTOP.STOPA
{
FOR i = 0 TO 30
{
nextSign[i] = f_Q[address][i] XOR sign[i + 1]