Specifications

Theory of Operation
EPC-100 Hardware Reference 4-7
watchdog time-out caused the hardware reset (as opposed to SYSRESET or power-
on reset). Depending on the value of a setup option the BIOS will then either HALT
the CPU or allow the boot process to continue.
Service of a watchdog interrupt is signaled to the counter by writing the register at
I/O 8150h. This will reset the counter and reset the signal driving IRQ9.
Flash Boot Device
The Intel E28F004BX-T is used as a Flash Boot Device (FBD). This is flash-
updatable BIOS containing the boot, main, and parameter blocks shown in Figure 4-2
and shadowed at the top of 32-bit address space. The use of the FBD allows
reprogramming of the main and parameter blocks of the BIOS.
The Plug-and-Play ESCD is also stored in the Boot-Block flash device in the block
addressed from FFFA0000h-FFFBFFFFh. This block is always accessible for re-
programming.
The boot block is NEVER reprogrammed by the user, even when the main and
parameter blocks are reprogrammed. The capability to program the boot block is
provided to facilitate changes by RadiSys manufacturing.
A “force recovery” jumper is provided that is connected to the P1-3 input of the
82C4PE keyboard controller. This jumper is readable by the boot block and can
force the boot block to initiate a recovery sequence at power-up should other
methods of initiating the sequence become inaccessible. (i.e. crisis recovery)
The system BIOS is shadowed in write protected DRAM at 000E0000h-000FFFFFh
during system boot.
The flash BIOS device is memory addressed and resides in the last 512KB of system
memory at address FFF80000h to FFFFFFFFh.
Keyboard/Mouse Controller
The Intel 82C42PE mouse/keyboard controller can interface to most standard PC
mice and keyboards with PS/2-style connectors. The keyboard controller uses
interrupt IRQ1 and the mouse uses IRQ12.