Campbell SC932C User manual

SC932C 9-Pin to
RS232-DCE Interface
User Guide
Issued 27.2.97
Copyright 1997 Campbell Scientific Ltd.

Guarantee
This equipment is guaranteed against defects in materials, workmanship,
and software. This guarantee applies for twelve months from date of
delivery. We will repair or replace products which prove to be defective
during the guarantee period provided they are returned to us prepaid. The
guarantee will not apply to:
•Equipment which has been modified or altered in any way without the
written permission of Campbell Scientific
•Batteries
•Any product which has been subjected to misuse, neglect, acts of God
or damage in transit.
Campbell Scientific will return guaranteed equipment by surface carrier
prepaid. Campbell Scientific will not reimburse the claimant for costs
incurred in removing and/or reinstalling equipment. This guarantee and
the Company’s obligation thereunder is in lieu of all other guarantees,
expressed or implied, including those of suitability and fitness for a
particular purpose. Campbell Scientific is not liable for consequential
damage.
Please inform us before returning equipment and obtain a Repair Refer-
ence Number whether the repair is under guarantee or not. Please state the
faults as clearly as possible, and if the product is out of the guarantee
period it should be accompanied by a purchase order. Quotations for re-
pairs can be given on request.
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marked on the outside of the package.
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which Campbell Scientific will charge to customers. In many cases, these
charges are greater than the cost of the repair.
Campbell Scientific Ltd,
Campbell Park, 80 Hathern Road,
Shepshed, Leicestershire, LE12 9RP, UK
Tel: [phone]
Fax: [phone]
Email: [email protected]
www.campbellsci.co.uk

Contents
1. Installation........................................................................ 1
2. Use with Intelligent Telephone Modems........................ 1
3. Other Applications........................................................... 2
Appendix A. SC932C to RS232 Device Connection
Details ..................................................................A-1
A.1 Cable for Connection to a 25-way DCE Interface .......................................A-1
A.2 Cable for Connection to a 9-way DCE Interface .........................................A-1
Appendix B. Technical Details of Special Modes of
Operation .............................................................B-1
B.1 Power Modes................................................................................................ B-1
B.2 Handshaking Lines....................................................................................... B-2
B.3 ‘Printer Only’ Output ................................................................................... B-2
B.4 Maximum Recall Interval............................................................................. B-2
Appendix C. Specifications...............................................C-1
Figures
1. SC932C Connected to RAD-SRM Short Haul Modem...................................... 1
A-1 Minimum Connections for SC932C to 25-way DCE Interface ...................A-1
A-2 Minimum Connections for SC932 to 9-way DCE Interface........................A-1
B-1 Connections for Using SC932C in ‘Printer’ Mode...................................... B-2
Tables
C-1 25-Pin Male Connector Pin-out ................................................................... C-2
C-2 9-Pin Male Connector Pin-out ..................................................................... C-2

1
SC932C 9-Pin to RS232-DCE Interface
The SC932C is used to interface a Campbell Scientific datalogger to modem devices that are
configured with an RS232 DCE (Data Communications Equipment) serial port. The most
common application is to allow the connection of a RAD-SRM short haul modem or third
party telephone modem to a datalogger.
The SC932C has the following features:
• Generates true RS232 signal levels to the DCE device, resulting in good noise immunity.
• Powered from the 5V supply of the datalogger, which is also available to provide power to
the DCE, if required for line-powered modems.
• Generates the required ring signal to wake up the datalogger, either when characters are
received or when there is a ring signal from the DCE.
• Allows simultaneous connection of synchronous devices (e.g. Storage Modules) to the
datalogger.
• Provides a mechanism for the datalogger to control the line state of intelligent modems
via DTR handshaking control.
• Convenient ‘jumperless’ design.
1. Installation
Use the SC12 ribbon cable (provided) to connect the datalogger’s 9-pin serial port
to the 9-pin connector on the SC932C. The SC932C can usually be connected to
the RS232 device by plugging the SC932C directly into the serial connector on the
RS232 device. No further configuration is normally required.
A typical application with a RAD modem would comprise:
Figure 1 SC932C Connected to RAD-SRM Short-Haul Modem
If the RS232 device does not have a suitable 25-way ‘D’ socket, you may need an
adaptor cable (see Appendix A).
2. Use with Intelligent Telephone Modems
If an ‘intelligent’ telephone modem is being used, configure it to allow the
SC932C to control its line status via the DTR line. This can prevent the modem
staying on-line unnecessarily, which can lead to excessive telephone charges and
also delay reconnection to the datalogger.
SC932C

SC932C 9-Pin to RS232-DCE Interface
2
Most phone modems can be configured to respond to the DTR line, although this is
not always the default setting. Although this feature is sometimes controlled by a
hardware configuration switch, more often it is a software setting, e.g. AT&D2&W
is the command for a Hayes-compatible modem to force the modem to follow the
DTR status.
3. Other Applications
The SC932C can be used in more specialist applications. Appendix B gives
installation details where even lower power consumption may be possible, and also
for applications where higher power outputs for the RS232 device are required.

A-1
Appendix A. SC932C to RS232 Device
Connection Details
This Appendix gives details of the cables required for connection of an SC932C to DCE type
RS232 devices, if the SC932C cannot be directly plugged into the 25-way DCE, RS232 socket.
A.1 Cable for Connection to a 25-way DCE Interface
A standard pin-to-pin cable is suitable. However, if a custom cable is to be made it
must make the following minimal connections:
Figure A-1 Minimum Connections for SC932C to 25-way DCE Interface
The link between pins 4 and 4 marked with the * may not be
required —see the section on low power operation in Appendix B.
A.2 Cable for Connection to a 9-way DCE Interface
Some newer modem-type devices are fitted with 9-way D connectors designed to
plug directly into 9-way serial ports as found on most ‘AT’ style PCs. Commercial
adaptor cables are available. If you use a custom made cable, it should have the
following connections:
Figure A-2 Minimum Connections for SC932C to 9-way DCE Interface
The link between pins 4 and 7 marked with the * may not be
required —see the section on low power operation in Appendix B.
NOTE
NOTE
25-Way D
Pin No.
25-Way D
Pin No.
25-Way D
Pin No.
2
2
3
2
33
23
77
75
2020
420
4*
4*
7*
4*
1
1
Cable Shield
Cable Shield
9-Way D
Pin No.
SC932C DCE Device
SC932C
DCE Device

B-1
Appendix B. Technical Details of Special
Modes of Operation
The SC932C is designed as a simple plug-in device with no internal jumpers. This Appendix
describes alternative modes of operation and also relates these to Campbell Scientific’s
original SC932 interface, for those users who are already familiar with that interface.
B.1 Power Modes
B.1.1 Normal Mode
In the normal mode of operation for the SC932C, a continuous supply of 4.3V is
available from the RTS line; this can be used as a source of power by some
interfaces, e.g. the RAD modem. The RTS and DTR lines both switch to >7V
when the SC932C becomes active. This mode will work for the majority of
applications. This mode is similar to the medium power setting of the SC932.
B.1.2 High Power Mode
A ‘high power’ setting can be forced, where RTS and DTR are held permanently
at >7V, by connecting pin 11 of the 25-way D connector to a voltage >3.5V DC.
To do this, add a link between pins 11 and 4 (RTS) on the SC932C’s 25-way D
connector. In this mode the SC932C consumes approximately 10-15mA
continuously. This mode is normally only necessary for devices which require
fully active input lines to provide a source of power to allow them to receive data
and transmit it to the SC932C.
In this mode the SC932C will not block the transmission of
synchronous data (e.g. Storage Module data) to the RS232 device.
This could cause a problem if, for example, the RS232 device is
reconfigured by the stream of binary data. Synchronous data is not
normally transmitted through the SC932C when in its normal mode
of operation.
B.1.3 Low Power Mode
The lowest power consumption can be achieved with RS232 devices which do not
need to source power from the SC932C. This is done by not connecting pin 11 or
the RTS line to the RS232 device. This is because a small current will flow from
the active RTS line into a standard RS232 RTS input on the device (normally
<1.5mA), even when the SC932C is inactive. Leaving RTS disconnected will only
work if the RS232 device does not require an active RTS line during
communication. Many high speed modems do have this requirement, by default,
but RTS/CTS handshaking can usually be turned off by software reconfiguration
(please refer to the modem manual).
NOTE

SC932C 9-Pin to RS232-DCE Interface
B-2
B.2 Handshaking Lines
In its normal power mode, and when inactive (i.e. the datalogger ME line is low)
the SC932C only holds the RTS line high to provide a source of power to line-
powered modems, such as the RAD modem.
The DTR line is controlled by the ME line of the datalogger. When ME is high the
DTR line is powered high (>7V), but when the ME line returns to a low state, the
DTR line enters a high impedance state; as far as the RS232 device is concerned,
this has the same effect as the DTR line going low. This transition can be used to
force the device to go off-line, if the device supports this.
This feature is useful for some telephone modems as it allows the datalogger to
force the modem off-line. The older SC932 only supports this type of handshaking
when operated in its low power mode.
The SC932C can be modified to support a form of RTS
handshaking for the support of some specialised half-duplex
interfaces. Please contact Campbell Scientific for further details.
B.3 ‘Printer Only’ Output
The SC932C can be used as a printer (PE/SDE enabled) device. However, unlike
the SC932 where this mode can be set using internal jumpers, the SC932C requires
a special connection in place of the normal direct SC12 cable. The connection to
the SC932C should be made up as follows:
Figure B-1 Connections for Using SC932C in ‘Printer’ Mode
(Other wires can be left connected or disconnected.)
With this connection the SC932C can be connected in parallel to another
Campbell Scientific modem-type device. However, as with the SC932, any data
output to synchronous devices (e.g. a Storage Module) will also be transmitted out
through the RS232 connection.
B.4 Maximum Recall Interval
From the time that the datalogger leaves communications mode (ME goes low),
there is a delay of approximately one second before serial or ring line activity from
NOTE
Datalogger
Pin No.
SC932C
9-Way D
Pin No.
1
1
2
2
4
55
69
9
No connection to SC932C
No connection to SC932C

Appendix B. Technical Details of Special Modes of Operation
B-3
the RS232 device will re-awaken the datalogger. This prevents spurious messages
from the RS232 device (such as ‘loss of carrier’ messages from a modem) waking
up the datalogger. The only consequence of this delay is that specialist software
which polls dataloggers at frequent intervals will not be able to wake the same
datalogger again during the delay period.
Campbell Scientific are aware of some modems which will re-trigger the ring line,
despite this delay. The only consequence of this is that the datalogger will remain
in communications mode for an extra 30 seconds after the end of the call; this will
waste a small amount of power and delay any output to a Storage Module.

C-1
Appendix C. Specifications
Data rates: up to 38,400 baud (limited by datalogger)
Size: 63 x 55 x 17mm (L x W x D), excluding mating D connectors
Operating environment: -25°C to +50°C, 0-95% RH (non-condensing)
Connector pin assignments: see Tables C-1 and C-2
Power requirements: sources power from datalogger 5V supply via 9-way
interface.
Typical current consumption
• <100µA with no RS232 load and pin 11 not connected
• 2.2mA with RAD-SRM and no communication
• 9.3mA with RAD-SRM, datalogger in communications mode, but low
communications activity
• 10.2mA with RAD-SRM, high communications activity
Current consumption when driving other RS232 modems will vary with the
number of lines connected and the input impedance of the inputs. With 3 inputs
connected (DTR, RTS and Tx from the SC932C), of the minimum 3kΩinput
impedance, and high communications activity the consumption may be up to
16mA.
RS232 output levels
• RTS 4.2 - 4.5V with 3kΩload –quiescent state (ME low)
• RTS full power 7 - 9V with 3kΩload (ME high)
• DTR 7.5 - 9.5V with 3kΩload (8.8V typical with RAD-SRM); short circuit
current 30mA typical
• Tx greater than ±5V with 3kΩload
RS232 input thresholds Rx and RI
• Input low 0.8V minimum
• Input high 2.4V maximum
• Input resistance 5KΩ
Pin 11, power control input thresholds
• Input low 1.3V maximum (normal power mode)
• Input high 3.5V maximum (to enable high power mode)
• Input resistance greater than 10kΩ
• Maximum input voltage 20V
Time-outs
• Minimum RING IN pulse width to generate a ring signal to the datalogger is
20µs
• Minimum delay between ME going low and RING IN enable is 0.5s (1s
typical)

SC932C 9-Pin to RS232-DCE Interface
C-2
EMC Specification
• Emissions BSEN 55022-1: 1995
• Immunity BSEN 50082-1: 1992
Connection Details
Table C-1 25-Pin Male Connector Pin-out
Pin No. I/O Name Description
1 GND Chassis Ground
2 out TXD SC932C transmits data on this line
3 in RXD SC932C receives data on this line
4 out RTS Held active by SC932C
7 GND Signal Ground
11 in PWR If held >3.5V will force SC932C into high power
mode
20 out DTR Held high if ME is high (see Appendix B)
Table C-2 9-Pin Male Connector Pin-out
Pin No. I/O Name Description
1in +5V Regulated 5V supply
2GND Ground
3out RING Ring signal to datalogger
4out RXD SC932C transmits on this line
5in ME Modem Enable
6in SDE Synchronous Device Enable/Print Enable
9in TXD SC932C receives on this line