User`s manual

User’s Manual 77

C.2.4 Reset Generator

The BL2000 uses a reset generator, U4, to reset the Rabbit 2000 microprocessor when the

voltage drops below the voltage necessary for reliable operation. The reset occurs between

4.50 V and 4.75 V, typically 4.63 V. The reset can be initiated either externally or by a

watchdog timeout (WDTOUT) on the Rabbit 2000 microprocessor.

Figure C-4. Reset Generator

NOTE: The Dynamic C function chkWDTO is not able to detect whether a watchdog

timeout has occurred on the BL2000. The GCSR status bits are read and stored by the

BIOS, and the reset status bit would normally change once a reset has occurred. How-

ever, since WDTOUT is tied to the reset generator, a watchdog timeout forces a hard-

ware reset, followed by the BIOS reading and storing the status bits corresponding to

power-up or reset.

To use chkWDTO to detect a watchdog timeout, remove D15 (located on the bottom

side of the BL2000).

R69

22 kW

RESET

GENERATOR

+5 V

/RESET

EXT

RESET

R151

100 kW

C24

100 nF

D17

WDTOUT

D15