RS232 DB9 Cable Problem

Good morning,

My name is Moraali. I am currently doing a project, but I have a problem on the cable communication issue.
FPGA is a Xilinx chip... You can get the info from

I am using Virtex4 ML401 (LX type)
The data sheet is on (look on the top left at sheet 12 )


So by using DMM, I found out that the PC and the Modem port is not loopback. Only the FPGA is loopback (pin 1,4and 6 is connected).

PC => Male Port
Modem => Female Port
FPGA => Male Port

I tested the cables (NOT the PC , NOT the MODEM , NOT the FPGA .... ONLY FROM THE CABLES USED) for three times and the result is below (for 9 Pin D Type ) :-

1) Presently what cable you are using in between PC and Modem? For your info, the flow control is none

PC Modem

2 => 2

3 => 3

5 => 5

2) And also what cable in between FPGA and PC?


2 => 3

3 => 2

5 => 5

3) I just tested between FPGA and Modem

FPGA Modem

2 => 2

3 => 3

5 => 5

I am not from engineering background. So, I am not so sure about labeling the Tx and Rx. I just assume that from the PC the 2 is Rx and the 3 is Tx. And 5 is definitely Gnd

a)Whether using any Hardware handshaking in between PC and Modem? - On both the 9 Pin D Type Connector check out the Pins

1- DCD
4 - DTR
6 - DSR
7 - RTS
8 - CTS

PC (Female) Modem (Male)

1 => 1

4 => 4

6 => 6

7 => 7

8 => 8


I only have you as my tutor. Please guide me. From the description ,
1)How can I rectify this problem? Should I buy a cable?
2)what type of cable should I purchase for the FPGA-Modem?

Please reply to me as soon as possible.

My contact:-
email:[email protected]

Thank you


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