EKF - Short Profile
EKF - Short Profile


CompactPCI Quad Serial Interface
RS-232 & RS-485 Across the Front Panel or by Rear-I/O

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CompactPCI Quad Serial Interface
Multi-Port RS-232/RS-485 Across the Front Panel or by Rear-I/O

Still the most common industrial data transfer method: the asynchronous serial interface according to RS-232 and RS-485.

The CompactPCI® card CU4-SOPRANO is provided with a quad UART. The line transceivers are individually configurable according to either RS-232E or RS-485.

The quad PCI UART is compatible to the widespread 16C550/650 series. Drivers are available by download for nearly all popular operating systems.

The CU4-SOPRANO is suitable for a variety of industrial applications, e.g. data acquisition, PXI measuring systems or process control.

CU4-SOPRANO • Quad Mutlti-Protocol Serial I/F


All ports are directly available from the CU4-SOPRANO front panel. Due to the height of 3U, the board is provided with four RJ45 Jacks. Integrated LEDs signal status information. An external adapter is available from RJ45 to DB9 (D-Sub connector) in order to maintain PC COM port compatibility.

Each port allows individual transceiver configuration according to either RS-232E or RS-485/422 by a single jumper. In addition, all 4 UART channels are wired as TTL-level signals to the rear connector J2 (option). By employing the CU9 rear-I/O transition board and PHY transceiver modules (CU7 and CU8 series), all ports are alternatively available from the back panel.

The drivers allow arbitrary names e.g. COM4..COM8 to be associated with the ports of the CU4-SOPRANO.


CR9-ADAPT 6U Front Panel Expansion Kit The CU4-SOPRANO is a 3U board (single size Eurocard). For usage in 6U systems, the front panel expansion kit CR9-ADAPT is available.

Block Diagram CU4-SOPRANO

Block Diagram CU4-SOPRANO

Feature Summary CU4-SOPRANO
Form Factor Single size CompactPCI style Eurocard (100x160mm2), front panel width 4HP (20.3mm)
Serial Interfaces
  • Asynchronous, serial protocol: 1 start bit; 7 or 8 data bits; 1 or 2 stop bits; optional even/odd parity; standard bit rates RS-232E up to 230.4 kbps
  • Quad PCI UART OX16PCI954, compatible with 16C550 (and in addition 16C450, 16C650, 16C750, 16C950), FIFO 1/16/128 Byte, automatic software flow control (XON/XOFF), automatic hardware flow control (CTS/RTS, DSR/DTR)
  • RS-232E or RS-485 (EIA/TIA-485) full-duplex (RxD/TxD) individually selectable for each port, dual-mode transceiver SP334 (up to 230.4kbps with RS-232, 921.6kbps and above with RS-485), 2kV ESD protection
  • 4 x RJ45 8-pos. I/O connectors in the front panel, integrated status LED display for RxD/TxD/RTS/CTS, external adapter RJ45 to DB9 available as accessory
  • Optional 4 x 10-position pin headers P1-P4, dual-row 2 x 5, 2.54mm pitch, suitable for optional attachment of a flat cable assembly with a DB9 connector at the opposite end (PC COM Port compatible when RS-232 is selected)
  • Additionally all UART ports available as buffered TTL signals across CompactPCI J2 connector for external transition-board CU9-BASE and PHY modules CU7/CU8 (option only, J2 must be omitted for 64-bit CPCI bus slots)
  • Serial drivers for Microsoft® Windows® 98/ME/NT4/2000/XP available by download
Parallel Interface (Option)
  • Optional pin header 2x13 position, 2.54mm pitch, for optional attachment of a flat cable assembly with a DB25 connector at the opposite end (PC DOS LPT port compatible)
  • Complies with IEEE-1284 EPP parallel port standard
  • Drivers for Microsoft® Windows® 98/ME/NT4/2000/XP available by download
  • Special board version CU4-P-SOPRANO available with front panel LPT printer port connector D-Sub 25
CompactPCI® CPCI bus master 32-bit 33MHz, +5V VIO interface (blue keying on J1 connector)
Rear I/O (Option) Optional J2 connector for attachment of a rear I/O transition module CU9-BASE
Power Requirements +5V ±5% 0.4A max.(optional consumption of external PHY-modules not included)
Thermal Conditions
Environmental Conditions
  • Operating temperature range 0°C ... +70°C (industrial temperature range on request)
  • Storage temperature range -40°C ... +85°C, max. gradient 5°C/min
  • Humidity 5% ... 95% RH non condensing
  • Altitude -300m ... +3000m
  • Shock 15g 0.33ms, 6g 6ms
  • Vibration 1g 5-2000Hz
EC Regulations
  • EN55022, EN55024, EN60950-1 (UL60950-1/IEC60950-1)
  • 2002/95/EC (RoHS)
MTBF 350,000h

specifications are subject to change without further notice

Assembly Drawing CU4-SOPRANO

Assembly Drawing CU4-SOPRANO

The quad UART is equipped with a flexible bit rate generator, which can be matched with a variety of oscillator frequencies for virtually any Baud rate. By default, the CU4-SOPRANO provides a 1.8432MHz oscillator.

Several UART registers affect the prescaler (CPR), the divisor and the sampling rate (TCR). It is the task of the drivers to manage these registers adequately.

Selected Oscillator Options
Oscillator (MHz) CPR (Prescaler) Clock effective (MHz) (MHz) max. Baud rate CPR=1 TCR=16 max. Baud rate CPR=1 TCR=4
1.8432 0x08 (1) 1.8432 115,200 460,800
3.6846 0x10 (2) 1.8432 230,400 921,600
7.3728 0x20 (4) 1.8432 460,800 1,843,200
14.7456 0x40 (8) 1.8432 921,600 3,686,400
18.432 0x50 (10) 1.8432 1,152,000 4,608,000
50.000 0xd9 (27.125) 1.8433 3,125,000 12,500,000

With an effective clock of 1.8432MHz and the sampling register TCR containing a value of 16, the typical Baud rates of a PC COM port can be achieved with the following divisor register values:

Selected Baud Rates
DLM:DLL Baud rate
0x0001 115,200
0x0002 57,600
0x0003 38,400
0x0004 28,800
0x0006 19,200
0x000c 9,600
0x0018 4,800
0x0030 2,400
0x0060 1,200
0x00c0 600
0x0180 300
0x0300 110
0x0900 50

RJ45 Front Panel Connectors CU4-SOPRANO

RJ45 Front Panel Jacks

RJ1..RJ4 (Front Panel)
RS-232 RJ1..RJ4 Pin # RS-485
DSR 1 do not use
DCD 2 do not use
DTR 3 do not use

External adapters from RJ45 to DB9 plug (male) or receptacle (female) are available, which are pre-assembled for custom configuring. By means of a pliers or inserting tool, the jumper wires from the RJ45 jack are ready to be pushed into the appropriate spot on the DB9 connector. The adapter itself must be connected to the corresponding RJ(1..4) jack of the CU4-SOPRANO. A suitable cable requires all 8 leads wired up straight forward 1:1. A short Ethernet patch cable could be used (avoid cross over patch cables, or old 4-wire Ethernet cables, or ISDN cables).

A male DB9 connector is required to emulate the serial RS-232 interface (COM port) of a desktop PC. The adapter must be wired up according to the scheme below. Due to one missing signal line, the modem-signal RI (Ring Indicator) is not available across the RJ45 jacks.

RJ45 to DB9 Adapter

RJ45 to DB9 Adapter

In order to connect the CU4-OPERA to a desktop PC, an adapter with a female DB9 connector can be directly attached to the COM port of the PC. The wiring scheme of the adapter emulates a null-modem cable. A typical configuration is shown in the diagram below.

RJ45 to DB9 Link Adapter

RJ45 to DB9 Link Adapter

There is no explicit standard in use for RS-485 across DB9 connectors, instead several proprietary solutions coexist. If the above adapter wiring scheme for RS-232 with a male DB9 would be used also for RS-485, the assignment of the differential signals can be derived from the diagram below:

RJ45 to DB9 RS-485

RJ45 to DB9 RS-485

Adapters RJ45 to D-SUB (also 15- or 25-position) are available from several distributors, but can also ordered directly from EKF. Please note, that the adapters are preassembled kits only, which must be configured (strapped) by the customer itself to fit his requirements. For volume quantities, please contact EKF in order to receive a quote on ready to use configured adapters.

Adapter Kit RJ45 to DB9 M

Adapter Kit RJ45 to DB9 Female

RJ45 to DB9 Adapter Kits

Is RS-485 a two-wire ore a three-wire system? It is most definitely a three wire system (four plus one wire with respect to full-duplex operation). The TIA standard (ANSI/TIA/EIA-485-A, page 15, A.4.1) requires the presence of a common return path between all circuit grounds along the balanced line for proper operation.

The TIA standard defines a maximum common mode voltage range from -7V to +12V on the signal lines A and B, measured against C (common ground). A TIA/EIA-485 system however with only two wires A and B (C generator and C receiver commons not connected) can result in an unpredictable common mode voltage superimposed on the interface lines A and B, caused either by electrostatic charging or electromagnetic interference.

A 2-wire system often may work though due to idle-line fail-safe resistors at the receiver inputs, which can be considered as a loosely coupled common ground. Nevertheless this operation mode cannot be recommended - what is working flawless in the laboratory may not work reliable under real conditions in an industrial environment.

Where do we get the third wire? Many times the outer cable shield is used as the third (fifth) wire. However, EKF recommends to use a two pair cable (three pairs for full-duplex operation), with one or both wires of the additional pair as the dedicated common ground. With respect to the wiring diagram above, connect these additional wires directly to the pin 5 of the DB9 connector for proper grounding. As an alternate, use a cable which provides an inner shield for each signal twisted pair. The inner shield can then be used for establishing the common ground between TIA/EIA-485 nodes.

Why a Third Wire is Needed as Common Ground - Read Article/Blog

Transceiver Schematics CU4-SOPRANO for a Single RS-232 Port

Transceiver Schematics CU4-SOPRANO for a Single RS-232 Port

Transceiver Schematics CU4-SOPRANO for a Single RS-485 Port

Transceiver Schematics CU4-SOPRANO for a Single RS-485 Port

The configuration of RS-232 or RS-485 is individually selectable for each serial port. When in RS-485 mode, the drivers may be enabled by RTS low, DTR low or fixed selection.

A jumper set on position JSER 1..4 configures the respective serial interface port transceiver to the RS-485 modus. A jumper removed forces the corresponding transceiver to the RS-232 mode.

Only when in RS-485 mode, the jumper positions JSER 5..6 are significant. Normally both jumpers 5 and 6 are removed. This enables permanently the differential line drivers, which is the suitable condition for the full-duplex transfer mode (also known as point-to-point or 2-point connection, both nodes can simultaneously send and receive data).

If more than two nodes are connected to a common bus, this operation mode is called RS-485 half-duplex (AKA party-line, only one node is allowed to send). The RxD and TxD lines are connected together in the party-line mode. A software protocol is required in order to pass a token to the active node, which sets its status signal RTS or DTR adequately. Jumpers JSER 5/6 are provided to control the behaviour of the RS-485 transmitters, in accordance to the settings in the driver software, either enabled by RTS, or DTR, or permanently enabled/disabled.

Jumper JSER
JSER 5 JSER 6 RS-485 Transmitters
removed removed permanently enabled
installed removed enabled by RTS
removed installed enabled by DTR
installed installed permanently disabled

Jumper JSER - Selection RS-232 or RS-485 Mode

Configuration Jumper JSER - Selection RS-232 or RS-485 Mode

The rear-I/O connector J2 is stuffed as an option only. In order to avoid potential conflicts, before installing the CU4-SOPRANO with the J2 populated, ensure that the system is not equipped with a P2 CompactPCI 64-bit expansion backplane. Otherwise, permanent damage to the board or to system components could occur.

The signal assignment of the optional J2 connector matches the transition board CU9-4-BASE. Across the transition board, rear-I/O PHY-modules of the CU7/CU8 series may be attached by means of a flat cable.

Rear-I/O Assembly CU9-4-BASE

Rear-I/O Assembly CU9-4-BASE

The TTL signals from J2/P2 are routed across the rear-I/O transition boards CU9-2-BASE or CU9-4-BASE to its shrouded pin headers H13..H16. By means of a short flat ribbon cable, the PHY modules CU7-RS485 or CU8-RS232 are attached. Up to four PHY modules CU7-RS485 and CU8-RS232 can be mounted at the 3U/12HP back panel of the CU9-2-BASE (CU9-4-BASE provides a 8HP back panel and is therefore preferred by most customers).

Available as a special version CU4-P-SOPRANO, the board is provided with a front panel printer port connector. This board version is not equipped with serial I/F transceivers and connectors, and hence is suitable solely as legacy parallel LPT port, aka Centronics printer I/F. The parallel port complies with the IEEE-1284 EPP parallel port standard. Drivers for Microsoft® Windows® are available by download.

CU4-P-SOPRANO - Special Version w. Front Panel LPT Connector

CU4-P-SOPRANO - Special Version w. Front Panel LPT Connector

Ordering Information
Ordering Number Short Description
CU4-1-SOPRANO 3U, CompactPCI quad serial interface, configurable alternatively as RS-232 or RS-485 (individually selectable by jumper), serial port connectors mounted in the front panel, w/o J2 connector, suitable for front panel I/O
CU4-2-SOPRANO Similar to CU4-1-SOPRANO, with J2 connector, suitable for rear I/O (J2 rear I/O backplane required)
CU4-P-SOPRANO Special version of the board, front panel LPT printer parallel port, no serial I/F available
CR9-5-ADAPT Front panel 6U expansion adapter, mounting kit
CU7-1-RS485 RS-485/RS-422 Rear-I/O PHY module, 1 Port, 2.5Mbps, 2-wire half-duplex (party line network), optically isolated, including flat cable assembly
CU7-2-RS485 RS-485/RS-422 Rear-I/O PHY module, 1 Port, 2 x 2.5Mbps, 4-wire full-duplex (point to point connection), optically isolated, including flat cable assembly
CU8-1-RS232 RS-232E rear-I/O PHY interface module, including flat cable assembly
CU9-4-BASE Transition board, interconnection between CU4-SOPRANO (J2) and rear-I/O PHY interface modules, 4 ports, 3U/8HP back panel included (custom specific back panels on request) Adapter, RJ45 jack to male D-Sub connector 9-pos., customer configurable, suitable e.g. for COM-port emulation Adapter, RJ45 jack to female D-Sub connector 9-pos., customer configurable, suitable e.g. for null-modem emulation
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