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JN-DS-JN5142 1v0
© NXP Laboratories UK 2012
At reset, the contents of this memory are copied into RAM by the software boot loader. The Flash and EEPROM
memory devices that are supported as standard through the JN5142 bootloader are given in Table 1. NXP
recommends that where possible one of these devices should be selected.
Manufacturer
Part Number
Size
Type
Micron
(Numonyx)
M25P10A
M25P05A
1 Mbit
512 kbit
Flash
Flash
Winbond
W25X20B
W25X10B
2 Mbit
1 Mbit
Flash
Flash
Microchip
25AA080
25AA160
25AA320
8 kbit
16 kbit
32 kbit
EEPROM
EEPROM
EEPROM
Table 1: Supported Flash and EEPROM Memories
Applications wishing to use an alternate Flash memory device should refer to Application Note [2]. This application
note provides guidance on developing an interface to an alternate device.
4.4.1 External Memory Encryption
The contents of the external serial memory may be encrypted. The AES security processor combined with a user
programmable 128-bit encryption key is used to encrypt the contents of the external memory. The encryption key is
stored in eFuse.
When bootloading program code from external serial memory, the JN5142 automatically accesses the encryption key
to execute the decryption process. User program code does not need to handle any of the decryption process; it is
transparent.
With encryption enabled, the time taken to boot code from external flash is increased.
4.5 Peripherals
All peripherals have their registers mapped into the memory space. Access to these registers requires 3 clock
cycles. Applications have access to the peripherals through the software libraries that present a high-level view of
the peripheral‟s functions through a series of dedicated software routines. These routines provide both a tested
method for using the peripherals and allow bug-free application code to be developed more rapidly. For details, see
[5].
4.6 Unused Memory Addresses
Any attempt to access an unpopulated memory area will result in a bus error exception (interrupt) being generated.