Symbol PDT 3400 Series, Руководство по продукции

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4-2
PDT 3400 Product Reference Guide
The segments in on-board Flash are grouped into “areas”, with each area consisting of one
or more segments. Typically, all segments in an area are erased and updated together. The
supported areas are IPL, BIOS, C:, D:, and user space.
Figure 4-1. Flash Memory Allocations
It is possible to erase and update an application stored in D: without updating the IPL, BIOS,
or C: drive. It is NOT possible, however, to update C: without updating D:. Because the
starting segment for D: falls on the next boundary after C: and that boundary is changeable,
updating C: means that D: must also be erased and updated. The user space likewise is
updated if C: or D: are updated, as the user space falls on the next boundary after D: (or C:,
if D: doesn’t exist). The IPL and BIOS can be updated independent of C: and D: because they
are always the same size and are always loaded in the same location.
For the PDT 3400, the IPL and BIOS are always loaded in the first two areas (the first 128K
segment) as shown in Figure 4-1. The third area, C:, is commonly used to store the DOS
operating system and common components such as scanning, RF, etc. The fourth area, D:,
can be used to store applications or data files. Any segments remaining comprise the user
space area and can be programmed individually as desired using the “Flash API”.
In calculating Flash requirements, remember that code such as DOS and applications can
only be stored in Flash. Applications and operating systems cannot execute out of Flash;
instead, they load from Flash into RAM and execute out of RAM.
IPL
BIOS
C:
D:
D: drive begins on
next boundary
after C: drive.
User space
begins on next
boundary after D:
drive.
128K
User Space
Flash - 128K
512 KB Flash
memory device (128
KB boundaries
2 MB (4 MB) Flash
memory device(s)
(64KB boundaries)
Note: This illustration shows a C: drive which exists totally in the 512 KB Flash device (128
KB boundaries). The D: drive and user space exists in the 2 MB (or 4 MB) Flash
device (64 KB boundaries).