Manual
High-Speed Microcontroller User’s Guide
Rev: 062210 13 of 176
monitor invokes a reset condition. This remains until power returns to normal operating voltage. The
power monitor also functions on power-up, holding the microcontroller in a reset state until power is
stable.
3.2.16 Interrupts
The high-speed microcontroller is capable of evaluating a number of interrupt sources simultaneously.
Each version of the high-speed microcontroller provides a different number of interrupt sources. Each
interrupt has an associated interrupt vector, flag, priority, and enable. Each interrupt can be globally
enabled or disabled.
3.2.17 Timing Control
The high-speed microcontroller provides an on-chip oscillator for use with an external crystal. This can
be bypassed by injecting a clock source into the XTAL 1 pin. The clock source is used to create machine
cycle timing (four clocks), ALE, PSEN, watchdog timer, and serial baud-rate timing. In addition, some
devices incorporate an on-chip ring oscillator which can be used to provide an approximately 2MHz to
4MHz clock source.
3.2.18 Real-Time Clock
The DS87C530 incorporates a real-time clock (RTC) that is accessed by the SFR locations. The RTC is
divided into hour, minute, second, and subsecond registers, and also incorporates a 65,536 day calendar.
Alarm registers allow the RTC to issue interrupts at a specific time once a day, or as a recurring alarm
every hour, minute or second. An external watch crystal and lithium power source allow the processor to
maintain timekeeping in the absence of V
CC
.
3.2.19 Feature Summary
The high-speed microcontroller family offers a combination of features and peripherals as shown in
Table 18-A. This user’s guide is designed as a comprehensive guide covering all features available in the
high-speed microcontroller family. The designer should investigate the specific data sheet to determine
which features are available on a particular device. Detailed information about newer members of the
product family may be provided in separate documents until they can be assimilated into the High-Speed
Microcontroller User’s Guide.