Ampro Corporation COM 830 - Manual (Page 52)

Chapter 3 Signals and Pinout Tables
46 Reference Manual COM 830
System Resources
System Memory Map
I/O Address Assignment
The I/O address assignment of the COM 830 module is functionally identical with a standard PC/AT. The
most important addresses and the ones that differ from the standard PC/AT configuration are listed in the
table below.
CAUTION The signals listed in the table above are used as chipset configuration straps
during system reset. In this condition (during reset), they are inputs that are
pulled to the correct state by either COM Express internally implemented
resistors or chipset internally implemented resistors that are located on the
module. No external DC loads or external pull-up or pull-down resistors
should change the configuration of the signals listed in the above table with
the exception of AC_SYNC and AC_SDOUT. External resistors may
override the internal strap states and cause the COM Express module to
malfunction and/or cause irreparable damage to the module.
AC_SYNC and AC_SDOUT can be used to switch PCI Express channels 1-4
between x1 and x4 mode. If both signals are each pulled-up (using 1K
resistors) to 3.3V at the rising edge of PWROK then x4 mode is enabled. x1
mode is used by default if these resistors are not populated.
Table 3-25. Memory Map
Address Range (decimal) Address Range (hex) Size Description
(TOM-192kB) – TOM N.A. 192kB ACPI reclaim, MPS
and NVS area **
(TOM-8MB-192kB) – (TOM-
192kB) N.A. 1 or 8MB VGA frame buffer *
1024kB – (TOM-8MB-192kB) 100000 – N.A N.A. Extended memory
869kB – 1024kB E0000 - FFFFF 128kB Runtime BIOS
832kB – 869kB D0000 - DFFFF 64kB Upper memory
640kB – 832kB A0000 - CFFFF 192kB Video memory and
BIOS
639kB – 640kB 9FC00 - 9FFFF 1kB Extended BIOS data
0 – 639kB 00000 - 9FC00 512kB Conventional memory
NOTE T.O.M. = Top of memory = max. DRAM installed
* VGA frame buffer can be reduced to 1MB in setup.
** Only if ACPI Aware OS is set to YES in setup