41CL Calculator Manual
© 2019 Systemyde International Corporation
69
Image Database
An entry in the Image Database consists of four words, and the format of the database is
set up to make adding new entries very easy. An unprogrammed Image Database entry
contains 0xFFFF in all four words. This is the default contents of Flash memory, where
the database is stored, which means that new entries can simply be added to the Image
Database without first needing to erase the Flash sector where the database is stored.
The
PLUG
functions will return a
NO ENTRY
error message if the user attempts to use
a module identifier corresponding to an unprogrammed database entry. An Image
Da
t
a
ba
s
e
e
nt
r
y
c
a
n
be
“
e
r
a
s
e
d”
by
wr
i
t
i
ng
0x0000
t
o
t
h
e first two words. In this case the
PLUG
functions will return a
NULL ENTRY
error message for the corresponding
module identifier.
To preserve backwards-compatibility with previous versions of the
41CL Extra
Functions
, the Image Database entries are addressed as a function of the first and fourth
characters of the module identifier only.
In order to limit the size of the database to 4K words only the characters
A
-
Z
,
1
-
5
and
9
(32 possibilities) are allowed for the first and fourth character of a module identifier.
When the first character of the module identifier is
9
and the last character is
A
-
Z
the
identifier is used as an alias for a secondary MMU configuration. Refer to the
41CL
Extreme Functions
manual for the details of this case. The remaining identifiers with a
first character of
9
are used for housekeeping. Any character is allowed for the second
and third characters of the module identifier.
The contents of each database entry are shown in the table below.
Image Data base
entry word
Address
LSBs
digit 3
meaning
digit 2
meaning
digit 1
meaning
digit 0
meaning
1
00
image group
image type
address<5>
2
01
page restriction
type modifier
address<4>
address<3>
3
10
always 0
always 0
character 2 of module identifier
4
11
always 0
always 2
character 3 of module identifier
Digits 3 and 2 of the first word in a database entry are used only by the
41CL Extreme
Functions
, to search the database by group. The table below shows the groups available
and their encoding in these two digits. Note that these two digits are always written as 00
when using the
IMDBINS
function (in the
41CL Extreme Functions
), so if you want to