Specifications

Little Board/486i Technical Manual
3–38
;----------------------------------------------------------
; Watchdog timer control program
;----------------------------------------------------------
MOV AH,0C3h ; Watchdog Timer BIOS function
MOV AL,nn ; Use “00” to disable, “01” to enable
; timer.
MOV BX,mm ; Selects time, in seconds
;(00-FFh; 1-255 seconds)
INT 15h
Ampro provides a simple DOS program that can be used from the command line or in a batch program to
manage the watchdog timer. It is called WATCHDOG, and is described in the Ampro Common Utilities
manual.
Note
Some versions of DOS turn off the real-time clock alarm at boot
time. If your DOS does this, make sure that your application
program enables the alarm function using this BIOS call.
3.17 POWERFAIL MONITOR
A hard reset is generated by a powerfail circuit if power falls below 4.5V.
If you have jumpered W20, the power management circuitry generates a power-fail Non-Maskable
Interrupt (NMI) if the power falls below 4.7V.
When an NMI occurs, the BIOS detects the NMI and displays the message “Power Fail NMI” on the
console. At this point you have two options via the keyboard. You can mask the NMI and continue (the
PC architecture provides a mask bit for the non-maskable interrupt), or reboot the system.
If you want to do something else with the NMI, you must provide your own power fail NMI handler and
patch the NMI interrupt vector address to install it.
3.18 SYSTEM MEMORY MAP
The Little Board/486i architecture allows it to address up to 64M bytes of memory. Table 3-14 shows how
this memory is used.
The DRAM, the byte-wide sockets, and ROM BIOS occupy the first megabyte (starting at 00000h). You
can install up to 64 megabytes of DRAM onboard with 1M, 4M, 8M, 16M, and 32M byte 72-pin SIMMs.