DS89C430 Maxim, DS89C430 Datasheet - Page 39

• Manufacturer Part Number: DS89C430
• Description: The DS89C430 and DS89C450 offer the highest performance available in 8051-compatible microcontrollers
• Manufacturer: Maxim

Figure 14. System Clock Sources
Bandgap-Monitored Interrupt and Reset Generation
The power monitor in the DS89C430 monitors the V
Whenever V
(WDCON.5) is set, causing the device to vector to address 33h. The power-fail interrupt status bit PFI (WDCON.4)
is set any time V
below V
power-on reset timeout before starting program execution. When V
processor is held in reset until V
is within tolerance and the clock source has had time to stabilize. Once the reset timeout period has elapsed, the
reset condition is removed automatically and software execution begins at the reset vector location of 0000h. The
power-on reset flag POR (WDCON.6) is set to logic 1 to indicate a power-on reset has occurred, and can only be
cleared by software.
When the DS89C430 enters stop mode, the bandgap, reset comparator, and power-fail interrupt comparator are
automatically disabled to conserve power if the BGS (EXIF.0) bit is set to logic 0. This is the lowest power mode. If
BGS is set to logic 1, the bandgap reference, reset comparator, and the power-fail comparator are powered up,
although in a mode that reduces their power consumption.
OSCILLATOR
RST
CRYSTAL
, a reset is issued internally to halt program execution. Following power-up, a power-on reset initiates a
CC
falls below V
CC
transitions below V
PFW
ENABLE
RING
, an interrupt is generated if the corresponding power-fail interrupt-enable bit EPFI
CC
4X/2X
CTM
> V
RST
PFW
and a delay of 65,536 oscillator cycles has elapsed, to ensure that power
, and can only be cleared by software once set. Similarly, as V
MULTIPLIER
DIVIDE 1024
OSCILLATOR
CLOCK
DS89C430/DS89C450 Ultra-High-Speed Flash Microcontrollers
RING
39 of 46
CC
pin in relation to the on-chip bandgap voltage reference.
CD0
CD1
CC
is first applied to the DS89C430, the
SELECTOR
MUX
SYSTEM
CLOCK
CC
falls