DA-660-8/16-CE User’s Manual
Introduction
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In addition, the FAT file system searches for free space sequentially when performing write
operations. As files are deleted, free storage space becomes more and more fragmented, making it
difficult to search. When a file is frequently updated, data is deleted and rewritten to the same
memory blocks over and over again. Eventually, the FAT file system would be unable to read those
blocks, causing the operating system to hang.
Although CompactFlash cards also have a life cycle, most use NAND flash memory with hardware
controllers that implement BBM. This feature allows the FAT file system to flag and skip any bad
blocks. Furthermore, there is much more storage space available on CompactFlash cards than on
the NOR flash memory. This space can be used cautiously to maximize the media’s life cycle. An
effective method is to create a large empty file (around 30 MB) to store log data. Data is written
evenly over the space, and when the end of the space is reached, the write operations start over
from the beginning of the space. This method reduces the number of write operations performed on
each block.
Storing Data in RAM vs. Flash Memory
Although data saved in RAM will be deleted when the system shuts down, RAM storage has the
advantage of faster read/write access and no life cycle issue.
For applications where important data is transmitted immediately and directly to a host, you can
store the necessary log data in RAM. After the host receives the data, the data does not need to be
retained and can be deleted.
Embedded computers have resource limits, so integrators need to determine when it is critical that
data be stored on one of the file systems. When it is necessary for data to be stored, the appropriate
file system should be used.
Hive-Based Registry
The registry for DA-660 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 kept on any file system. This
eliminates the need for performing backup and restore on power off.
RS-232/422/485 Serial Ports
The DA-660 embedded computer comes with two embedded serial ports, named COM1 and
COM2. COM1 is hidden inside the box case for debugging purposes when developing firmware.
COM2 is used as the console port. Although the console port can be used when developing
applications (e.g., data acquisition and control), we suggest that you always use the serial ports
located on the front of the device for your applications, and reserve COM2 for console access.
The additional serial ports are named COM3, COM4, etc., reading from left to right. The ports are
designed for reliable, high-speed data transmission. The ports are 3-in-1 (i.e., they can be set for
RS-232, RS-422, or RS-485) to make them suitable for many different applications. Each of the
ports supports a baudrate up to 921600 bps.
