Black Box ME253C-R2, ME253A-R2, ME255A-R2, ME251C-R3, ME255AE-R2 User Manual

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Mailing address: Black Box Corporation, 1000 Park Drive, Lawrence, PA 15055-1018
Web site: www.blackbox.com • E-mail: [e-mail]

CUSTOMER

SUPPORT

INFORMATION

DECEMBER 2001

ME251A-R3

ME251AE-R3

ME251C-R3
ME253A-R2

ME253AE-R2

ME253C-R2
ME255A-R2

ME255AE-R2

ME255C-R2

Synchronous Modem

Eliminator (SME-4M)

SME-4

DSR TXD CTS

B B B

RI CON LB

CTS TXD DSR

A A A

FCC STATEMENT

1

FEDERAL COMMUNICATIONS COMMISSION

AND

INDUSTRY CANADA

RADIO FREQUENCY INTERFERENCE STATEMENTS

This equipment generates, uses, and can radiate radio frequency energy and if not installed and used
properly, that is, in strict accordance with the manufacturer’s instructions, may cause interference to radio
communication. It has been tested and found to comply with the limits for a Class A computing device in
accordance with the specifications in Subpart B of Part 15 of FCC rules, which are designed to provide
reasonable protection against such interference when the equipment is operated in a commercial
environment. Operation of this equipment in a residential area is likely to cause interference, in which
case the user at his own expense will be required to take whatever measures may be necessary to correct
the interference.

Changes or modifications not expressly approved by the party responsible for compliance could void the user’s
authority to operate the equipment.

This digital apparatus does not exceed the Class A limits for radio noise emission from digital apparatus set out in the Radio
Interference Regulation of Industry Canada.

Le présent appareil numérique n’émet pas de bruits radioélectriques dépassant les limites applicables aux appareils numériques
de la classe A prescrites dans le Règlement sur le brouillage radioélectrique publié par Industrie Canada.

Synchronous Modem Eliminator (SME-4M)

2

INSTRUCCIONES DE SEGURIDAD (Normas Oficiales Mexicanas Electrical Safety Statement)

1. Todas las instrucciones de seguridad y operación deberán ser leídas antes de que el aparato eléctrico sea operado.

2. Las instrucciones de seguridad y operación deberán ser guardadas para referencia futura.

3. Todas las advertencias en el aparato eléctrico y en sus instrucciones de operación deben ser respetadas.

4. Todas las instrucciones de operación y uso deben ser seguidas.

5. El aparato eléctrico no deberá ser usado cerca del agua—por ejemplo, cerca de la tina de baño, lavabo, sótano
mojado o cerca de una alberca, etc..

6. El aparato eléctrico debe ser usado únicamente con carritos o pedestales que sean recomendados por el fabricante.

7. El aparato eléctrico debe ser montado a la pared o al techo sólo como sea recomendado por el fabricante.

8. Servicio—El usuario no debe intentar dar servicio al equipo eléctrico más allá a lo descrito en las instrucciones de
operación. Todo otro servicio deberá ser referido a personal de servicio calificado.

9. El aparato eléctrico debe ser situado de tal manera que su posición no interfiera su uso. La colocación del aparato
eléctrico sobre una cama, sofá, alfombra o superficie similar puede bloquea la ventilación, no se debe colocar en
libreros o gabinetes que impidan el flujo de aire por los orificios de ventilación.

10. El equipo eléctrico deber ser situado fuera del alcance de fuentes de calor como radiadores, registros de calor, estufas
u otros aparatos (incluyendo amplificadores) que producen calor.

11. El aparato eléctrico deberá ser connectado a una fuente de poder sólo del tipo descrito en el instructivo de
operación, o como se indique en el aparato.

12. Precaución debe ser tomada de tal manera que la tierra fisica y la polarización del equipo no sea eliminada.

13. Los cables de la fuente de poder deben ser guiados de tal manera que no sean pisados ni pellizcados por objetos
colocados sobre o contra ellos, poniendo particular atención a los contactos y receptáculos donde salen del aparato.

14. El equipo eléctrico debe ser limpiado únicamente de acuerdo a las recomendaciones del fabricante.

15. En caso de existir, una antena externa deberá ser localizada lejos de las lineas de energia.

16. El cable de corriente deberá ser desconectado del cuando el equipo no sea usado por un largo periodo de tiempo.

17. Cuidado debe ser tomado de tal manera que objectos liquidos no sean derramados sobre la cubierta u orificios de
ventilación.

18. Servicio por personal calificado deberá ser provisto cuando:

A: El cable de poder o el contacto ha sido dañado; u

B: Objectos han caído o líquido ha sido derramado dentro del aparato; o

C: El aparato ha sido expuesto a la lluvia; o

D: El aparato parece no operar normalmente o muestra un cambio en su desempeño; o

E: El aparato ha sido tirado o su cubierta ha sido dañada.

TRADEMARK STATEMENT

3

TRADEMARKS USED IN THIS MANUAL

Any trademarks mentioned in this manual are acknowledged to be the property of the trademark owners.

Synchronous Modem Eliminator (SME-4M)

4

Contents

Chapter Page

1. Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5

2. Description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6

3. Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8

3.1 LED Displays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10

4. Digital Loopback Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12

5. Application Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13

6. RS-232 Interface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14

7. Nonstandard Transmission Speeds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17

CHAPTER 1: Specifications

5

1. Specifications

AC Power — 115 VAC, 60 Hz or 230 VAC, 50 Hz, 10 watts

Wallmount No load output voltage: 18 VAC nominal

Transformer Output — Voltage at rated current 16 + 0.5 VAC rated

Load Current 0.13 amps (part number PS154)

Size — Standalone Unit: 1.8"H x 5.5"W x 8.5"D (4.5 x 13.9 x 21.5 cm)

Weight — Standalone Unit: 2 lb. (0.9 kg)

Enclosure — High-impact plastic

Connectors — (2) DB25 female, mounted on rear panel

Interface — RS-232C (CCITT V.24/V.28) serial synchronous or asynchronous

Indicators — (6) LEDs: TX Data, CTS and DSR for each of the two ports

External Controls — RI button, loopback switch and DSR control

Operating Environment — 32 to 122°F (0° to 50°C), Up to 95% relative humidity, non-condensing

RM008 Rack Dimensions — 5.22"H x 19"W x 9.25"D (13.2 x 48.2 x 23.4 cm)

(For Standard Equipment Rack)

RM008 Rack Weight (with no cards installed) — 9.5 lb. (4.3 kg)

Synchronous Modem Eliminator (SME-4M)

6

2. Description

The SME-4M Synchronous Modem Eliminator is designed to replace two modems in point-to-point
applications. As shown below, a single SME-4M allows asynchronous, synchronous or bisynchronous
communications between two items of data terminal equipment (DTE) over EIA RS-232C cable.

In the synchronous mode, the SME-4M operates at speeds up to 38,400 bps, 56,000 bps or 64,000 bps
depending on the model. In either synchronous or asynchronous mode, the SME operates
transparently.

The small size and light weight of the SME-4M minimize logistics problems and simplifies installation
and replacement in the field. Since no special tools are required, the SME-4M unit is designed for
o-it-yourself installation.

Six indicators and three front panel switches facilitate operation and do-it-yourself troubleshooting.
The indicators (three for each item of DTE) monitor Transmitted Data, Data Set Ready and Clear To
Send signals. The front panel switches control Data Set Ready (DSR) and Ring Indicator (RING)
signals as well as select the digital loopback (DLB) test mode.

Figure 2-1. Typical Point-to-Point Application with Modems

Figure 2-2. Typical Point-to-Point Application without Modems

ASYNC OR

SYNC HOST

MODEM

MODEM

ASYNC OR

SYNC TERMINAL

DIALUP OR

LEASED LINE

ASYNC OR

SYNC HOST

ASYNC OR

SYNC HOST

ASYNC OR

SYNC HOST

(ECN25C)

RS-232 CABLE

(ECN25C)

RS-232 CABLE

CHAPTER 2: Description

7

Figure 2-3. Location of Controls, Indicators and Straps

CTS B

TXD B

DSR B

LB

CON

RI

DSR A

TXD A

CTS A

AC

PWR

Y1

W7

DSR-B

REM

LOC

50ms

10ms

0ms

CTS-B

DELAY

W3

50ms

10ms

0ms

CTS-B

DELAY

W4

U9

U7

U8

U10

U5

U2

W8

CD-B

ON

SW

W9

DSR-A

REM

LOC

REM

LOC

CTS-A

W5

CD-A

ON

SW

W6

CTS-B

ON

SW

PORT A

PORT B

Synchronous Modem Eliminator (SME-4M)

8

3. Installation

Proceed as follows to install the SME-4M:

1. Remove the release screw located on the bottom center of the unit and separate the cover
from the unit.

2. Plug in the cord from the transformer to the male power connector, J3, on the card.
Do not plug the transformer into an AC outlet.

3. Using the cables supplied with your terminal’s or computer’s ports, connect them to the
25-pin connectors (J1 and J2) at the rear of the unit. (If no cables are available, use pin-for-pin
EIA RS-232C cables having at least pins 1-8, 15, 17, 20, 21, 22, and 24 wired (these are the
minimum number of pins that can be connected for the unit to function properly).

4. Select the operating mode by installing the speed selection strap (W2 in Figure 2-3) to async
or the desired synchronous speed as shown below. For more information see Chapter 7.

PART NUMBER SPEED STRAP POSITION

ME251A-R3, 1200, 2400, 4800 Shown on board
ME251AE-R3, 9600, 19,200 or
ME251C-R3 38,400 bps

ME253A-R2, 56,000 bps a
ME253AE-R2,
ME253C-R2

ME255A-R2 64,000 bps a
ME255AE-R2
ME255C-R2

5. For synchronous operation, select the clock source for both DTE devices. For external
clock to be supplied by the device connected to Port A, install the “XA” external clock strap.
For external clock to be supplied by the device connected to Port B, install the “XB”
external clock strap.

6. The following strapping will work in most configurations including IBM

®

System AS/400™,

System 36, and System 38:

• CTS A = SW • CTS Delay = 10 MS

• CTS B = SW • CD Delay = 10 MS

• CD A = SW • DSR A = Local

• CD B = SW • DSR B = Local

Set all front panel pushbuttons in the OUT position.

CHAPTER 3: Installation

9

NOTE

The IBM device parameters should be set for non-switched/leasedline.

If different settings are required, see steps 7 through 10.

7. Select the CTS control by installing both the “A” and “B” CTS constant/switched straps.

In the switched position, a CTS signal is generated when the SME-4M receives an RTS signal
(in the digital loopback test mode, the control signals always will be ON). In the constant
position, CTS and Carrier Detect (of the respective port), and Signal Quality of the other
port are always ON.

8. For switched CTS applications, select the CTS delay for Port A and B by installing the CTS

delay selection straps. Delays of 0, 10, and 50 milliseconds are available.

9. Select the DSR control by installing the “A” and “B” DSR remote/local straps. In the remote

position, the DSR signal is generated when the other port receives a DTR signal. In the local
position, DSR is always on.

10. The CD (Carrier Detect) option is controlled by setting the “A” and”B” Switched or Constant

straps. In the Switched position, a CD signal is generated when the other port receives a RTS
signal. In the Constant position, CD is always on.

NOTE

If the CTS options are set to Constant, the CD options have no effect.

11. Install the top cover.

12. Connect the communication devices to ports A and B.

13. Plug in the transformer.

14. If the local DSR control was selected by the configuration straps, the CON front panel switch

must be in the OUT position to turn DSR ON. Set the CON switch to the IN position to turn
DSR OFF.

15. If required by your application, press then release the momentary RING switch to send Ring

Indicator signal.

16. Observe the indicators for each item of DTE to monitor the status.

17. The SME-4M is now ready for operation.

Synchronous Modem Eliminator (SME-4M)

10

3.1 LED Displays

TXD ON Transmitted Data in space

OFF Transmitted Data in mark

TXA ON data flow from port B to port A

OFF no data flow from port B to port A

TXB ON data flow from port A to port B

OFF no data flow from port A to port B

DSR ON Data Set Ready signal ON

OFF Data Set Ready signal OFF

DSR A ON indicates a DSR signal (pin 6) out from port A

OFF indicates no DSR signal (pin 6) out from port A

DSR B ON indicates a DSR signal (pin 6) out from port B

OFF indicates no DSR signal (pin 6) out from port B

NOTE

In DSR remote mode, the DSR LEDs also indicate the reception of DTR

(pin 20) from the opposite port.

CHAPTER 3: Installation

11

CTS ON Clear To Send signal ON

OFF Clear To Send signal OFF

CTS A ON indicates a CTS signal (pin 5) out from port A

OFF indicates no CTS signal (pin 5) out from port A

CTS B ON indicates a CTS signal (pin 5) out from port B

OFF indicates no CTS signal (pin 5) out from port B

NOTE

In the CTS switched mode, the CTS LEDs also indicate the reception

of RTS (pin 4) from the same port.

Synchronous Modem Eliminator (SME-4M)

12

4. Digital Loopback Test

The digital loopback test is for asynchronous applications only. Proceed as follows to initiate the test.

1. Press the loopback switch (the switch must remain in the IN position) on the front panel
to loopback at the digital interfaces for both devices connected to the SME-4M.

2. Enter data at the terminal or computer. The data should be returned to the DTE device
exactly as it was entered.

3. Release the DLB switch (the switch must remain in the OUT position) to end the test.

CHAPTER 5: Application Notes

13

5. Application Notes

Figure 5-1. Typical IBM Application

For most applications (including the one shown in Figure 5-1) the following configuration

is recommended:

1. Select the appropriate baud rate for which the system is configured (modem clocking).

2. Since the modem eliminator is always connected, it is recommended to configure
the computer equipment for point to point, non-switched phone line (leased line).

3. The following strapping will work in most configurations including IBM System AS/400,
System 36, and System 38:

• CTS A = SW • CTS Delay = 10 MS

• CTS B = SW • CD Delay = 10 MS

• CD A = SW • DSR A = Local

• CD B = SW • DSR B = Local

Set all front panel pushbuttons in the OUT position.

NOTE

The IBM device parameters should be set for non-switched/leased line.

4. With DSR A and B configured “Remote”, the DSR A and B LEDs will indicate the opposite
ports DTR signal (generated by the connecting equipment). Therefore, if DSR A is not lit,
check the computer device connected to B and vice-versa. The connected device may not
be ready to communicate, may be configured incorrectly or may have a cable problem.

The SME-4M printed circuit card is made to be installed in the RM008 rack. The rack fits into a
standard 19" equipment rack and can hold up to 16 SME-4M printed circuit cards. The RM008
rack is available for either 115 VAC, 60 Hz or 230 VAC, 50 Hz power.

ASYNC 36

HOST

SME-4M

PORT A PORT A

5294 OR 5251

MODEL 12

Synchronous Modem Eliminator (SME-4M)

14

6. RS-232 Interface Pinning

Table 6-1 RS-232 Interface Pinning

PIN CIRCUIT DESCRIPTION SIGNAL TYPE DIRECTION

1 AA Protective Ground Ground —

2 BA Transmitted Data Data To DCE

3 bb Receive Data Data From DCE

4 CA Request To Send Control To DCE

5 CB Clear To Send Control From DCE

6 CC Data Set Ready Control From DCE

7 AB Signal Ground Ground

8 CF Data Carrier Detect Control From DCE

9 — + DC Test Voltage — —

10 — - DC Test Voltage — —

11 — Unassigned — —

12 SCF Secondary Data Control From DCE

Carrier Detect

13 SCB Secondary Clear Control From DCE

To Send

14 SBA Secondary Transmit Data To DCE

Data

15 DB Transmit Signal Timing From DCE

Element Timing (DCE)

16 SBB Secondary Receive Data From DCE

Data

17 DD Receiver Signal Timing From DCE

Element Timing

CHAPTER 6: RS-232 Interface Pinning

15

Table 6-1. RS-232 Interface Pinning (continued)

PIN CIRCUIT DESCRIPTION SIGNAL TYPE DIRECTION

18 — Local Loopback Test To DCE

19 SCA Secondary Request Control To DCE

To Send

20 CD Data Terminal Ready Control To DCE

21 CG Signal Quality Control From DCE

Detector

22 CE Ring Indicator Control From DCE

23 CH Data Signal Rate Control To DCE

Selector (DTE)

or

CI Data Signal Rate Control From DCE

Selector (DCE)

24 DA Transmitter Signal Timing To DCE

Element Timing (DTE)

25 — Test Mode/No Signal — —

Synchronous Modem Eliminator (SME-4M)

16

NOTE

The above chart shows all pins on the DB25 connector. The SME-4 only uses

Pins 1 through 8, 15, 17, 20, 21, 22, and 24.

FIgure 6-1. RS-232 Interface Female Connector

SIGNAL PIN PIN SIGNAL
DISTINATION NUMBER NUMBER DESTINATION

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

PROTECTIVE GROUND

TRANSMITTED DATA

RECEIVED DATA

REQUEST TO SEND

CLEAR TO SEND

DATA SET READY

SIGNAL GROUND/COMMON RETURN

RECEIVED LINE SIGNAL DETECTOR

+ VOLTAGE

- VOLTAGE

SECONDARY RECEIVED LINE SIGNAL INDICATOR

SECONDARY CLEAR TO SEND

SECONDARY TRANSMITTED DATA

DCE TRANSMITTER SIGNAL ELEMENT TIMING

SECONDARY RECEIVED DATA

RECEIVER SIGNAL ELEMENT TIMING

SECONDARY REQUEST TO SEND

DATA TERMINAL READY

SIGNAL QUALITY DETECTOR
RING INDICATOR

DATA SIGNAL RATE SELECTOR

DTE TRANSMITTER SIGNAL ELEMENT TIMING

CHAPTER 7: Nonstandard Transmission Speeds

17

7. Nonstandard Transmission Speeds

The SME-4M can be configured to operate at some nonstandard data transmission speeds depending
upon the model and the frequency of the installed crystal. To set the SME-4M for one of these different
speeds, configure the unit according to the chart below.

Table 7-1. SME-4M Synchronous Transmission Speeds

ME251 ME253 ME255

CRYSTAL 2.4576 MHz 1.792 MHz 2.048 MHz
FREQUENCY

STRAP
POSITION TRANSMISSION RATE (bps)

a 76,800 56,000 64,000

b 153,600 112,000 128,000

38,400 38,400 28,000 32,000

19,200 19,200 14,000 16,000

9600 9600 7000 8000

4800 4800 3500 4000

2400 2400 1750 2000

1200 1200 875 1000

1000 Park Drive • Lawrence, PA 15055-1018 • 724-746-5500 • Fax [phone]

© Copyright 2001. Black Box Corporation. All rights reserved.