Customizing The Board 5-4
5.4 Expanded and Extended Memory
Memory on the board consists of two areas: memory below 1 MB (0-640KB) referred to as
the standard or base memory, and memory located above 1 MB which is either
Expanded
or
Extended
memory (memory located between 640KB and 1 MB is reserved for
shadowing. This is described later in this section).
Expanded and Extended
memory refer to the mapping scheme that is used to access
memory above 1 MB in real mode. Since DOS requires real mode to operate, different
techniques are available. The TEK-AT4L
PLUS
offers the following options:
5.4.1
Expanded Memory
In Expanded memory mode, hardware is used to remap a defined area of memory. This
mode is driven by standard software commonly referred to as the LIM Standard or EMS.
A hardware-specific device driver (supplied with your single board computer) is loaded in
the CONFIG.SYS file to setup the software in order for it to access memory above 1 MB.
5.4.2
Extended Memory
In Extended memory mode, the CPU's own protected mode is used to access the memory
above 1 MB. This mode requires that the software jump into protected mode, perform the
transfer and return back to real mode. This is available through the BIOS using INT 15h
function 87h.
5.5 Memory Mode
Above 1MB can be defined either as EMS or Extended.
If EMS is used, the EMS hardware must be enabled, and the EMS driver loaded.
. EMS is enabled by entering SETUP at boot up
. Type the following command (or its equivalents) in the CONFIG.SYS file:
DEVICE=EMM386.EXE
5.6 Shadow RAM
As previously mentioned, memory between 640KB and 1MB is used for
Shadow RAM
or
Shadowing
. This is simply the process of copying EPROM based code, such as the BIOS
and BIOS extensions, into DRAM (which is located in the same physical memory map).
Shadowing
allows your code to run faster.
WARNING
: If Shadow RAM is enabled, the RAM memory used for shadowing is no
longer available as EMS or Extended memory.
Summary of Contents for TEK-AT4L Plus
Page 7: ...PRODUCT DESCRIPTION 1 PRODUCT OVERVIEW 2 ONBOARD SUBSYSTEMS...
Page 9: ...Product Overview 1 2 TEK AT4LPLUS Block Diagram...
Page 26: ...Installing Devices 6 3 CONNECTOR LOCATION...
Page 35: ...Setting Jumpers 8 3 JUMPER LOCATIONS...
Page 36: ...Setting Jumpers 8 5 TABLE 8 1 Jumper Settings W1 W11...
Page 37: ...Setting Jumpers 8 6 TABLE 8 2 Jumper Settings W12 W19 W26...
Page 38: ...Setting Jumpers 8 7 TABLE 8 3 Jumper Settings W20 W25 SW1 SW2...
Page 41: ...APPENDICES A PRODUCT SPECIFICATIONS B BOARD DIAGRAMS C CONNECTOR PINOUTS...
Page 43: ...Board Diagrams B 1 B 1 TEK AT4LPLUS Assembly Diagram Top View...
Page 44: ...Board Diagrams B 3 B 2 TEK AT4LPLUS Mounting Holes...
Page 45: ...Board Diagrams B 5 B 3 TEK AT4LPLUS Mechanical Specifications...
