
UM10800
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© NXP Semiconductors N.V. 2016. All rights reserved.
User manual
Rev. 1.2 — 5 October 2016
371 of 487
NXP Semiconductors
UM10800
Chapter 25: LPC82x Flash In-System and In-Application Programming
Table 309. Code Read Protection options
Name
Pattern
programmed in
0x0000 02FC
Description
NO_ISP
0x4E69 7370
Prevents sampling of the ISP entry pin for entering ISP mode. The ISP entry pin is available for
other uses.
CRP1
0x12345678
Access to chip via the SWD pins is disabled. This mode allows partial flash update using the
following ISP commands and restrictions:
•
Write to RAM command should not access RAM below 0x1000 0300. Access to
addresses below 0x1000 0200 is disabled.
•
Copy RAM to flash command can not write to Sector 0.
•
Erase command can erase Sector 0 only when all sectors are selected for erase.
•
Compare command is disabled.
•
Read Memory command is disabled.
This mode is useful when CRP is required and flash field updates are needed but all sectors
can not be erased. Since compare command is disabled in case of partial updates the
secondary loader should implement checksum mechanism to verify the integrity of the flash.
CRP2
0x87654321
Access to chip via the SWD pins is disabled. The following ISP commands are disabled:
•
Read Memory
•
Write to RAM
•
Go
•
Copy RAM to flash
•
Compare
When CRP2 is enabled the ISP erase command only allows erasure of all user sectors.
CRP3
0x43218765
Access to chip via the SWD pins is disabled. ISP entry by pulling the ISP entry pin LOW is
disabled if a valid user code is present in flash sector 0.
This mode effectively disables ISP override using the ISP entry pin. It is up to the user’s
application to provide a flash update mechanism using IAP calls or call re-invoke ISP
command to enable flash update via UART.
Caution: If CRP3 is selected, no future factory testing can be performed on the device.
Table 310. Code Read Protection hardware/software interaction
CRP option
User Code
Valid
ISP entry pin
at reset
SWD enabled
Part enters
ISP mode
partial flash
update in ISP
mode
None
No
x
Yes
Yes
Yes
None
Yes
High
Yes
No
NA
None
Yes
Low
Yes
Yes
Yes
CRP1
Yes
High
No
No
NA
CRP1
Yes
Low
No
Yes
Yes
CRP2
Yes
High
No
No
NA
CRP2
Yes
Low
No
Yes
No
CRP3
Yes
x
No
No
NA
CRP1
No
x
No
Yes
Yes
CRP2
No
x
No
Yes
No
CRP3
No
x
No
Yes
No