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 k
W
U4
RESET
GENERATOR
+5 V
/RESET
EXT
RESET
R151
100 k
W
C24
100 nF
D17
WDTOUT
D15
Summary of Contents for BL2020
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