User`s manual

COMHP 7404/-D25 CyberResearch

Serial Communications

Technical Description

The CyberResearch

COMHP 7404 provides a PCI interface adapter with 4 RS-232/422/485 asynchronous serial ports for

industrial automation and control applications.

The COMHP 7404 utilizes the 16C864 UART. This chip features programmable baud rates, data format, interrupt control

and industry leading 128-byte transmit and receive FIFOs.

Connector Pin Assignments

RS-422/485 (DB 9 Male)

Signal Name Pin # Mode

GND Ground 5

TX + Transmit Data Positive 4 Output

TX- Transmit Data Negative 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- Clear To Send Negative 8 Input

RS-232 (DB-9 Male)

Signal Name Pin # Mode

GND Ground 5

TD Transmit Data 3 Output

RTS Request To Send 7 Output

DTR Data Terminal Ready 4 Output

RD Receive Data 2 Input

CTS Clear To Send 8 Input

DSR Data Set Ready 6 Input

DCD Data Carrier Detect 1 Input

RI Ring Indicator 9 Input

Technical Note: Please terminate any control signals that are not going to be used. The most common way to do this is

connect RTS to CTS and RI. Also, connect DCD to DTR and DSR. Terminating these pins, if not used, will help ensure you

get the best performance from your adapter.