14

www.corebai.com

CBM705/CBM706/CBM707/CBM708

OPERATION INSTRUCTION

APPLICATIONS INFORMATION

A typical application circuit is shown in Figure 18. The un-regulated dc input supply is

monitored using PFI via the resistive divider network. Resistor R1 and Resistor R2 must be

selected so when the supply voltage drops below the desired level (such as 8V), the voltage on

PFI drops below the 1.25V threshold, thereby generating an interrupt to the microprocessor.

Monitoring the preregulator input provides additional time to execute an orderly shutdown

procedure before power is lost.

Figure 18. Typical Application Circuit

Microprocessor activity is monitored using WDI. This is driven using an output line from the

processor. The software routines toggle this line at least once every 1.60 seconds. If a problem

occurs and this line is not toggled, WDO goes low and a nonmaskable interrupt is generated.

This interrupt routine can clear the problem.

If in the event of inactivity on the WDI line, a system reset is required, WDO must connect to

MR as shown in Figure 19.

Figure 19. RESET From WDO