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emPC-CXR
(
Hardware Manual
)
•
FPGA expansion subsystem
©
Janz Tec AG
Rev. V1.2
6.4
NVRAM
The emPC-CXR implements an integrated nvSRAM memory. This device implements 128kx8
NVRAM. The NVRAM is a fast SRAM style device, however there is no need for battery maintenance.
Address
Description
BAR5 + 0x080000..0x09FFFF
NVRAM area
Table 13: NVRAM address (128KByte NVRAM)
The NVRAM can be accessed by 8-, 16- and 32 bit operations (read and write).
If NVRAM is accessed by 16/32 bit operations, these are not atomic. In case of power
down, it might happen that only parts of the 16/32 bit value are stored in the nvSRAM.
Also notice that the PCI interface has buffers. Even if the write operation has been
finished from CPU point of view, it might not have been saved into the memory. To make
sure data has reached the memory, you need to read back the latest written content.