On-Board Memory; Serial And Parallel Ports - Xycom XVME-654 Manual

On-board Memory

DRAM Memory
The XVME-654 has one 72-pin SIMM memory site, providing up to 32 Mbytes of
DRAM. The memory site can be populated by standard fast page mode memory or
extended data out memory (EDO). EDO memory is designed to improve DRAM read
performance. Using EDO memory improves the back-to-back burst timing to 2-2-2 from
3-3-3 of standard memory.
Flash BIOS
The XVME-654 board provides a location for a Flash BIOS that is used for system
ROM, video ROM, and an optional Ethernet boot ROM. The Flash socket supports a 256
Kbyte x 8-bit or 512 Kbyte x 8-bit device.
Table 1-1 describes the memory map for the 512 Kbyte Flash device.
Device Address
70000h-7FFFFh
60000h-6FFFFh
50000h-5FFFFh
48000h-4FFFFh
40000h-47FFFh
30000h-3FFFFh
20000h-2FFFFh
10000h-1FFFFh
08000h-0FFFFh
00000h-07FFFh
An on-board switch controls which part of the Flash device is loaded into shadow
DRAM. This allows you to update half the Flash device and still retain a copy of the
original BIOS if the update is not successful or the BIOS is not correct. You can
determine which section of the BIOS is being used by writing to port 219h (bit 2=0) and
then reading bit 3 from port 219h. If bit 3 returns a zero, the lower portion of the BIOS is
being used.

Serial and Parallel Ports

PC/AT peripherals include two high-speed, RS-232C, 16550-compatible serial ports and
one bidirectional Centronics-compatible parallel port.
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Table 1-1. 512 Kbyte Flash Memory Map
Device System Address
System BIOS F0000h-FFFFFh also FFFF0000h-FFFFFFFFh
System BIOS E0000h-EFFFFh also FFFE0000h-FFFEFFFFh
Option ROM D0000h-DFFFFh also FFFD0000h-FFFDFFFFh
Option ROM C8000h-CFFFFh also FFFC8000h-FFFCFFFFh
Video BIOS C0000h-C7FFFh also FFFC0000h-FFFC7FFFh
System BIOS F0000h-FFFFFh also FFFF0000h-FFFFFFFFh
System BIOS E0000h-EFFFFh also FFFE0000h-FFFEFFFFh
Option ROM D0000h-DFFFFh also FFFD0000h-FFFDFFFFh
Option ROM C8000h-CFFFFh also FFFC8000h-FFFCFFFFh
Video BIOS C0000h-C7FFFh also FFFC0000h-FFFC7FFFh
Chapter 1 – Introduction
1-3