User`s manual
PK2200 Subsystems s 23
Processor Core
The PK2200s processor core is composed of the CPU, microprocessor
supervisor/watchdog timer, battery-backed static RAM, EPROM/flash
EPROM, EEPROM, and RTC.
CPU
The PK2200 is available with either 9.216 MHz or 18.432 MHz CPU
clock speeds. The 18.432 MHz clock improves system performance and
allows baud rates up to 11,500 bps. PK2200s with the 9.216 MHz option
are limited to 57,600 bps. The system clock speed is a 16-bit value stored
at location 0x108 in the EEPROM. The clock speed is expressed in
multiples of 1200 Hz. The value read for 9.216 MHz clocks is 7,680 and
for 18.432 MHz clocks the value read is 15,360.
Microprocessor Supervisor/Watchdog Timer
The microprocessor supervisor/watchdog timer provides the following
functions for the PK2200.
Power monitoring for the processor. Protects the system during
brownouts and fluctuating power conditions. The supervisor
provides a power-fail output that can be monitored by the
processor, allowing the processor to save important information
before a complete power-fail and then halt operation until power
is fully restored.
Battery backup for the static RAM. Allows data to remain intact
even when power is removed from the PK2200.
Watchdog timer function. Resets the system in the event of a
software or hardware error that causes the processor to enter an
infinite loop.
Static RAM
Static RAM is normally used to store program data. RAM can also be
used to store program code. This is especially useful during software
development because it allows quick program changes without having to
change EPROMs.
EPROM/Flash EPROM
EPROMs offer a low-cost, permanent medium for storing program code
and constant data. Once the application program is fully functioning and
debugged, an EPROM can be programmed and installed. EPROMs can
be quickly and easily duplicated, and are easy to install.