ENIGMA XM88422 Digital Receiver
Version 1.50
19
CPM Ports
The ENIGMA digital receiver is equipped with two
RS232 serial and one Centronics parallel port. The
two serial ports have some very important differences
in function. The port functions and operation will be
detailed in this section.
Serial Port 1 (COM1)
The Serial Port 1, or as referred shortly COM1, is the
main communication port of the CPM Unit. Its main
task is to establish communication and report events
to the automation software on the central station
computer as described in the Serial Communication
section.
The secondary task of this port is the serial
programming of the receiver (See The CPM Module,
Serial Programming). When programming the
receiver from the serial ports, the CPM Unit can be
operated normally and does not have to be switched
to protected mode. Therefore, serial programming of
the receiver is recommended if possible.
The speed and data byte protocol of the COM1 port
can be set at the Setup, Serial Setup, COM1 Setup
section of the menu, as described before in section
Serial Setup. The default setting is 9600 bps, 8
databits, no parity, 1 stopbit.
Serial Port 2 (COM2)
The Serial Port 2, or as referred, COM2 is the
secondary serial port of the receiver. In normal
operation, it can be used to receive serial protocols
from other receivers (E.g. SurGard or another
ENIGMA). All the events received on COM2 are
stored in the CPM as they would received on the
virtual Line Card 00, and will be listed together with
the events received on the physical Line Cards of the
receiver.
With this ability, the receiver can be used to upgrade
older systems, or to link multiple receivers through
the serial ports and act as one, big receiver from the
view of the central station computer. This option
could be useful, when the central station computer
has only limited number of serial ports, and more
receivers has to be used in the system.
The speed and data byte protocol of COM2 can be
set similarly as the COM1’s. The default setting is
9600 bps, 8 databits, no parity, 1 stopbit.
Serial Communication
When the CPM receives a message from a Line
Card, from COM2 or there is a CPM status event, it
records the event in the memory buffer then forwards
the event to COM1 and awaits acknowledge signal
from the computer. Normally a positive acknowledge
is received, and the receiver steps to the next
reportable event.
If no acknowledge or negative acknowledge signal is
received, the CPM will try to resend the event 3 more
times. If all attempts fail, the receiver generates a
“COM1 Error” event, and will keep it in the memory
buffer and repeatedly try to send the event until it
succeeds. The CPM Unit can store up to 4096 events
in its memory buffer if the connection to the central
station computer is broken.
If the receiver succeeds to send the event after a
communicatio
n failure, a “COM1 Restored” event will
be recorded. After the communication channel is
restored, the CPM will send all pending reportable
events from its memory buffer to the computer. This
method
provides
reliable
and
supervised
communication between the CPM and the central
station computer.
The COM1 port is also supervised with heart-beat
signals. The heart-beat signals are used to test the
communication channels between the receiver and
the central station computer when there is no
reportable event in the memory buffer. It works that
way, that the receiver sends so called heart-beat
signals to the computer in a programmed time and
requires acknowledge for that. If the acknowledge is
missing or negative, it assumes that the computer is
failed, and gives
“COM1 Error” message.
If the automation software is not compatible with
heart-beat supervision, the heart-beat signals can
also be turned off (See CPM Options).
Serial Protocols
The receiver uses different serial communication
protocols for the connection to the automation
software on the central station computer. Which
protocol is used depends on which format has the
event that has to be forwarded to the computer. The
serial protocols used by the ENIGMA receiver are the
following
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