User`s manual

PK220024
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 Subsystems
Even though slightly more expensive than standard EPROM, flash
EPROM offers the following benefits.
• In-system programmability.
• Remote downloading of program code and data.
• Easier to reprogram.
• Erases quicker without a special eraser.
EEPROM
EEPROM offers a separate area for storing permanent or semi-permanent
information such as clock speed, network address, calibration coeffi-
cients, and installation data. The EEPROM can be write-protected using
a jumper, which prevents data from being accidentally overwritten.
Real Time Clock (RTC)
The RTC provides the application program with the current date and time
of day. The PK2200’s battery keeps the RTC running even when the
power is off. The RTC is accurate to about one second a day and
compensates for leap years and variances in the number of days in each
month.
Digital Inputs
The PK2200’s 16 digital inputs (PN01 through PN16) are flexible and
robust. Configurable pull-up or pull-down resistors and high voltage
protection circuits allow the inputs to detect switch contacts, relay
contacts, outputs from open-collector transistor devices, logic level
outputs, and high voltage outputs. In addition, two inputs may be used for
generating interrupts and another two may be used for high-speed
counting. The protected digital inputs have the follwoing features:
• Nominal input voltage range of –20 V to +24 V.
• Protection against overloads over the range of –48 V to +48 V.
• Logic level detection.
• Configurable pull-ups and pull-downs. Jumper the digital inputs
in groups of eight to pull up to +5 V or down to GND through
4.7 kΩ resistors.
The nominal voltage range for the protected digital inputs is -20 V to
+24 V. The inputs are protected against overvoltages in the range -48 V
to 48 V; however, inputs should not be regularly subjected to voltages
outside the nominal voltage range.
Logic-level signals can also be detected using the digital inputs. The
logic threshold is nominally 2.5 V. The maximum guaranteed low
voltage is 1.25 V. The minimum guaranteed high voltage is 3.75 V.