background image

COMHP 7404/-D25  

CyberResearch

® 

Serial Communications 

 

2

 

©Copyright 2010 

CyberResearch, Inc.

 

 
 

Card Setup 

RS-485 Enable Modes 

RS-485 is ideal for multi-drop or network environments. RS-485 requires a tri-state driver that will allow the electrical 
presence of the driver to be removed from the line. The driver is in a tri-state or high impedance condition when this occurs. 
Only one driver may be active at a time and the other driver(s) must be tri-stated. The output modem control signal 

R

equest 

T

S

end (RTS) is typically used to control the state of the driver. Some communication software packages refer to RS-485 as 

RTS enable or RTS block mode transfer. 

One of the unique features of the 

COMHP 7404 

is the ability to be RS-485 compatible without the need for special software 

or drivers. This ability is especially useful in Windows and other protected mode environments where the lower level I/O 
control is abstracted from the application program. This ability means that the user can effectively use the 

COMHP 7404 

in 

an RS-485 application with existing (i.e. standard RS-232) software drivers. 

Switches SW1 - SW4 are used to control the RS-485 mode functions for the driver circuit. The selections are ‘RTS’ enable 
(silk-screen ‘RT’) or ‘Auto’ enable (silk-screen ‘AT’). The ‘Auto’ enable feature automatically enables/disables the RS-485 
interface.  The ‘RTS’ mode uses the ‘RTS’ modem control signal to enable the RS-485 interface and provides backward 
compatibility with existing software products. 

Position 3 (silk-screen ‘NE’) of these switches is used to control the RS-485 enable/disable functions for the receiver circuit 
and determine the state of the RS-422/485 driver. The RS-485 ‘Echo’ is the result of connecting the receiver inputs to the 
transmitter outputs. Every time a character is transmitted; it is also received. This can be beneficial if the software can handle 
echoing (i.e. using received characters to throttle the transmitter) or it can confuse the system if the software does not. To 
select the ‘No Echo’ mode select silk-screen position ‘NE’. 

Typically, each end of the RS-485 bus must have a line-terminating resistor (RS-422 terminates the receive end only). A 
120-ohm resistor is across each RS-422/485 input in addition to a 1K-ohm pull-up/pull-down combination that biases the 
receiver inputs. Only the ends of an RS-485 network should have the 120-Ohm terminating resistor. Position 4 (silk-screen 
‘T’) selects the presence of the 120-Ohm termination resistor across the input data pins (RX+/RX-). To add the termination 
select the ‘On’ position, to remove it select the ‘Off’ position. 

For RS-422/530/449 compatibility set all switches ‘Off’. Examples on the following pages describe some of the valid 
settings for SW1-SW4. 

Содержание COMHP 7404

Страница 1: ...128 Byte FIFO Buffer with 4 DB 9M Cable or 4 DB 25M Cable D25 Model USER S MANUAL VER 2 0C Jun 10 No part of this manual may be reproduced without permission CyberResearch Inc Hwww cyberresearch com...

Страница 2: ......

Страница 3: ...ed for identification purposes only and may be trademarks and or registered trademarks of their respective companies NOTICE CyberResearch Inc does not authorize any CyberResearch product for use in li...

Страница 4: ...COMHP 7404 D25 CyberResearch Serial Communications Revision History Revision Description Date of Issue 1 0 Initial Release May 1 2007 2 0C Revision June 9 2010 iv Copyright 2010 CyberResearch Inc...

Страница 5: ...ERATING SYSTEM INSTALLATION 7 For Windows Users 7 Other Operating Systems 7 SYSTEM INSTALLATION 7 TECHNICAL DESCRIPTION 8 CONNECTOR PIN ASSIGNMENTS 8 RS 422 485 DB 9 Male 8 RS 232 DB 9 Male 8 CONNECTO...

Страница 6: ...Echo and the termination resistor in circuit 3 Figure 3 Switches SW1 SW4 RS 485 Auto Enabled with Echo and no termination resistor in circuit 3 Figure 4 Switches SW1 SW4 RS 485 RTS Enabled with No Ec...

Страница 7: ...485 mode our special auto enable feature allows the RS 485 ports to be viewed by the operating system as a COM port This allows the standard COM driver to be utilized for RS 485 communications Our on...

Страница 8: ...AT The Auto enable feature automatically enables disables the RS 485 interface The RTS mode uses the RTS modem control signal to enable the RS 485 interface and provides backward compatibility with e...

Страница 9: ...ON OFF AT RT NE T Figure 2 Switches SW1 SW4 RS 485 Auto Enabled with No Echo and the termination resistor in circuit 1 2 3 4 ON OFF AT RT NE T Figure 3 Switches SW1 SW4 RS 485 Auto Enabled with Echo...

Страница 10: ...in circuit 1 2 3 4 ON OFF AT RT NE T Figure 5 Switches SW1 SW4 RS 485 RTS Enabled with Echo and no termination resistor in circuit Address and IRQ selection The COMHP 7404 is automatically assigned re...

Страница 11: ...on to aid in the configuration of your electrical interface E5 E6 Port 2 RS 232 RS 422 E7 E8 Port 1 RS 232 RS 422 RS 422 485 E1 E2 Port 4 RS 232 RS 422 E3 E4 Port 3 RS 232 RS 422 RS 232 E5 E6 Port 2 R...

Страница 12: ...reen D1 Baud Rates and Divisors for the DIV1 mode The following table shows some common data rates and the rates you should choose to match them if using the adapter in the DIV1 mode For this Data Rat...

Страница 13: ...ppropriate section of the Serial Utilities Software System Installation The COMHP 7404 can be installed in any of the PCI expansion slots and contains configuration options for each port that must be...

Страница 14: ...gative 3 Output RTS Request To Send Positive 6 Output RTS Request To Send Negative 7 Output RX Receive Data Positive 1 Input RX Receive Data Negative 2 Input CTS Clear To Send Positive 9 Input CTS Cle...

Страница 15: ...m Connector Pin Assignments RS 232 RS 422 485 DB 37 Male Port 1 2 3 4 RS 422 485 RS 232 RX DCD 37 10 28 1 RX RD 36 11 27 2 TX TD 35 12 26 3 TX DTR 34 13 25 4 GND GND 33 14 24 5 RTS DSR 18 29 9 20 RTS...

Страница 16: ...ring All Systems Printed Circuit boards are built to U L 94V0 rating and are 100 electrically tested These printed circuit boards are solder mask over bare copper or solder mask over tin nickel Power...

Страница 17: ...unique IRQ While the CyberResearch adapter does allow the sharing of IRQs many other adapters i e SCSI adapters on board serial ports do not The IRQ is typically selected via an on board header block...

Страница 18: ...lanced interface meaning that a single electrical signal is compared to a common signal ground to determine binary logic states A voltage of 12 volts usually 3 to 10 volts represents a binary 0 space...

Страница 19: ...as electrical characteristics that allow for 32 drivers and 32 receivers to be connected to one line This interface is ideal for multi drop or network environments RS 485 tri state driver not dual sta...

Страница 20: ...op bits usually 1 1 5 or 2 An extra bit used for error detection is often appended before the stop bits Remain Idle or next start bit Odd Even or Unused STOP P BIT 5 to 8 Data Bits Idle state of line...

Страница 21: ...CyberResearch Serial Communications COML 4232U D25 Appendix D Silk Screen 4 2 6 5 CyberResearch Inc 15 25 Business Park Drive P 203 643 5000 F 203 643 5001 Branford CT USA www cyberresearch com...

Страница 22: ...C Directive Statement Products bearing the CE Label fulfill the requirements of the EMC directive 89 336 EEC and of the low voltage directive 73 23 EEC issued by the European Commission 16 Copyright 2...

Страница 23: ...urements of the signals you are trying to measure as well as the signals on the board module or power supply 4 Isolate problem areas that are not working as you expected 5 Have the source code to the...

Страница 24: ...COMHP 7404 D25 CyberResearch Serial Communications Intentionally Blank 18 Copyright 2010 CyberResearch Inc...

Страница 25: ...urchased and in lieu of all other warranties expressed implied or statutory including but not limited to any implied warranty of merchant ability or fitness and all other obligations or liabilities of...

Страница 26: ...COMHP 7404 D25 CyberResearch Serial Communications Intentionally Blank 20 Copyright 2010 CyberResearch Inc...

Страница 27: ......

Страница 28: ...CyberResearch Inc 25 Business Park Drive Branford CT 06405 USA P 203 643 5000 F 203 643 5001 www cyberresearch com...

Отзывы: