BL4S200 User’s Manual
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3.9 Memory
3.9.1 SRAM
The RabbitCore modules used with the BL4S200 boards all have 512 KB of data SRAM.
The RabbitCore modules on the BL4S200 and BL5S220 boards also have 512 KB and
1 MB of fast program execution SRAM.
3.9.2 Flash Memory
The RabbitCore modules used with the BL4S200 boards have 512 KB or 1 MB of flash
memory.
NOTE:
Rabbit recommends that any customer applications should not be constrained by
the sector size of the flash memory since it may be necessary to change the sector size
in the future.
Writing to arbitrary flash memory addresses at run time is also discouraged. Instead,
define a “user block” area to store persistent data. The functions
writeUserBlock()
and
readUserBlock()
are provided for this.
3.9.3 VBAT RAM Memory
The tamper detection feature of the Rabbit microprocessor can be used to detect any
attempt to enter the bootstrap mode. When such an attempt is detected, the VBAT RAM
memory in the Rabbit microprocessor is erased. The serial bootloader on the RabbitCore
module on the BL4S200 model uses the bootstrap mode to load the SRAM, which erases
the VBAT RAM memory on any reset, and so it cannot be used on this model for tamper
detection.
3.9.4
microSD™
Cards
The RabbitCore module on the BL4S200 model supports a removable
microSD™ Card
up
to 1 GB to store data and Web pages. The
microSD™ Card
is particularly suitable for
mass-storage applications, but is generally unsuitable for direct program execution.
Unlike other flash devices, the
microSD™ Card
has some intelligence, which facilitates
working with it. You do not have to worry about erased pages. All
microSD™ Cards
sup-
port 512-byte reads and writes, and handle any necessary pre-erasing internally.
Figure 20 shows how to insert or remove the
microSD™ Card
. The card is designed to fit
easily only one way — do
not
bend the card or force it into the slot. While you remove or
insert the card, take care to avoid touching the electrical contacts on the bottom of the card
to prevent electrostatic discharge damage to the card and to keep any moisture or other
contaminants off the contacts. You will sense a soft click once the card is completely
inserted. To remove it, gently press the card towards the middle of the RabbitCore module
on the BL4S200 model — you will sense a soft click and the card will be ready to be
removed. Do not attempt to pull the card from the socket before pressing it in — otherwise
the ejection mechanism will get damaged. The ejection mechanism is spring-loaded, and
will partially eject the card when used correctly.