CP347 – User Guide, Rev. 1.3
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Functional Description
2.1.
General Information
The CP347 serial communications controller board is the realization of a low cost solution for industrial automation
communication purposes and represents the implementation of a serial communication controller board at the basic
OSI levels.
The main functions implemented on the CP347 board are the OSI Layer 2 data link control for RS232, RS422 and
RS485 communication purposes, and the OSI Layer 1 physical signal level adaptation for the RS232, RS422 and RS485
interfaces. The RS422 interface is realized for full duplex (4-wire) and the RS485 Interface is realized for half duplex
(2-wire) operation.
The physical layer adaptation (OSI Layer 1) of the TTL interface signals is realized independently for each channel via
corresponding on-board RS232, RS422/RS485 transceivers. Each of the four serial communication links are
configured individually for serial interface operation per hardware and software, including the serial line termination
for balanced serial communication.
2.2.
Specifics
The OSI Layer 2 functions for serial communication are handled entirely by the Exar XR17D154 serial I/O controller.
This controller handles all the on-board serial communication tasks related to the OSI Layer 2, and also the data
transfer to the system host CPU over the CompactPCI bus.
For the various operation types, configuration of the serial communication links as well as serial line termination for
differential communication (RS422/RS485) is accomplished via hardware and software. The four serial I/O channels
are independent and can be configured individually for RS232, RS422/RS485 serial communication.
The data transfer operation of the serial channels is indicated at the front panel by four channel related pairs of LEDs,
for receive and transmit operations.
The communication functions including the RS232, RS422 and RS485 serial I/O functions are tied to the host system
via the standard PCI interface provided directly on the Exar XR17D154. Logical control of the CP347 serial
communication operation is accomplished via the Exar XR17D154 command and status registers that can be accessed
independently for each channel directly from the PCI side.
The CP347 serial I/O board is provided with a 37-pin D-Sub connector providing the signals for all four serial I/O
channels. In order to provide separate serial I/O channeling, a front panel adapter can be connected to the 37-pin
front panel connector. This adapter terminates on the user side with four, male, 9-pin, D-Sub connectors (one per
serial I/O channel).
In addition, the CP347 is galvanic isolated between the system side and the serial I/O front panel D-Sub connector for
all four channels. This is accomplished with digital isolators using the iCoupler® technology. This is especially useful
in industrial environments, where voltage potential differences between the different transmission stations can
occur. Using this technology GND compensating currents can be avoided or minimized and the digital system side,
where expensive components such as CPU are located, is protected against noise transients.
An optional 1 Kbit EEPROM can be assembled to store the vendor’s ID and model number, and the sub-vendor’s ID and
product model number. If an EEPROM is assembled, the PCI controller reads four word data from the EEPROM’s first
four word locations and places those values into the PCI configuration space registers for chipset identification.
Additionally, the EEPROM can store proprietary data. If no EEPROM is assembled, the PCI controller uses the default
value of the PCI controller’s vendor and device ID. The IDs are stored in the configuration space for chipset
identification during the auto-configuration sequence.
2.3.
Board Interfaces
The CP347 serial I/O board provides a 37-pin D-Sub connector with signals for all four serial I/O channels.
Additionally, in order to provide separate serial I/O channeling, it is possible to connect a front panel adapter to the
37-pin D-Sub front panel connector. This adapter terminates on the user side with four male 9-pin D-Sub connectors,