User`s manual

UC-7122/7124 User’s Manual Introduction
An SD card has its own life cycle. Since most SD cards are made from a NAND Flash, their
hardware controllers implement BBM. This feature allows FAT to skip bad blocks if they exist.
Furthermore, the memory space of an SD card is much larger than that of the NOR Flash. Using
this space cautiously will ensure that its life cycle is not exceeded. When creating a file for storing
log data, we suggest creating a large empty file (e.g., 30 MB), and then writing data evenly to that
space. When the space is used up, the program rewinds the write operations. As a result, the
number of write operations to each block is reduced.
Using a RAM File System instead of a Flash File System
Even though data in the RAM file system will be deleted after shutting off the power, using the
RAM file system has several advantages over using the Flash file system, including faster
read/write access and not needing to deal with the life cycle issue.
For important applications that relay data back to the host directly, you should write the necessary
log data to the RAM file system. After the host accesses the data, the application erase the data,
freeing up the memory space for further use.
The embedded computer has limited resources, and designers should decide if storing data in a file
system is really necessary. If it is necessary, be sure to choose the most appropriate file system.
Hive-based Registry
The registry for the UC-7122/7124 is a hive-based registry instead of a RAM-based registry. The
hive-based registry stores registry data inside files, or hives, which can be stored in any file system.
This eliminates the need for performing backup and restoring power.
Each file or hive contains a collection of registry data. The hive-based registry is split into two
hives: the system hive, which contains all system data, and the user hive, which contains all data
pertinent to one particular user. The UC-7122/7124 embedded computer is a multi-user system,
and accordingly contains several user hives. A user’s hive will be mounted on logon and
dismounted on logoff.
Inserting an SD Card into the Computer
The UC-7122/7124 is equipped with an SD slot. When an empty SD card is inserted into the slot,
the computer automatically formats it to the FAT system. This process takes a few minutes to
complete. After an SD card is inserted, the embedded computer will create a directory named
“StorageDisk” under the root directory. The “StorageDisk” directory controls access to the SD
storage space. The embedded computer will create a directory called “StorageDisk2” if another
USB storage device is plugged in at a later time.
Connecting a USB Mass Storage Device to the Computer
The USB mass storage device is considered to be highly portable between your PC and a computer
that does not support the TFAT system. We suggest that you format your devices with the FAT
format. When the first USB storage device is plugged into the slot on the back of the computer, a
directory named “USBDisk” under the root directory is created in the internal file system as a link
to the storage device. The embedded computer will create a directory called “StorageDisk2” if
another SD storage device is plugged in at a later time.
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