© NXP Laboratories UK 2012
JN-DS-JN5142 1v0
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4.2 RAM
The JN5142 contains 32KBytes of high speed RAM. It can be used for both code and data storage and is accessed
by the CPU in a single clock cycle. At reset, a boot loader controls the loading of segments of code and data from an
external memory connected to the SPI port, into RAM. Software can control the power supply to the RAM allowing
the contents to be maintained during a sleep period when other parts of the device are un-powered. Typical RAM
contents are shown in Figure 7.
MAC Data
Interrupt Vector Table
Application
CPU Stack
(Grows Down)
0x04000000
0x04008000
MAC Address
Figure 7: Typical RAM Contents
4.3 OTP eFuse Memory
The JN5142 contains a total of 29bytes of eFuse memory; this is a One Time Programmable (OTP) memory that can
be used to support a 40-bit MAC ID (For a 64-bit MAC ID, the 24 bit company ID, OUI, can be stored in the external
memory) and a 128-bit AES security key. A limited number of bits are available for customer use for storage of
configuration information; configuration of these is made through use of software APIs.
For further information on how to program and use the eFuse memory, please contact technical support via the on-
line tech-support system.
Alternatively, NXP can provide an eFuse programming service for customers that wish to use the eFuse but do not
wish to undertake this for themselves. For further details of this service, please contact your local NXP sales office.
4.4 External Memory
An external memory with an SPI interface may be used to provide storage for program code and data for the device
when external power is removed. The memory is connected to the SPI interface using select line SPISEL0; this
select line is dedicated to the external memory interface and is not available for use with other external devices. See
Figure 8 for connection details.
JN5142
Serial
Memory
SPISEL0
SPIMISO
SPIMOSI
SPICLK
SS
SDO
SDI
CLK
Figure 8: Connecting External Serial Memory