Connection between MAX 232 (level converter) and DB 9 pin connectors

[Li Gang]

Hi,
Is it normal for an MAX 232 (level converter) to be connected to two DB 9 pin connectors?

Thanks in advance.

Li

 

[hexreader]

MAX232 contains two transmitters and two receivers.

If your RS232 connection only requires Tx and Rx, without hardware handshakes, then one MAX232 can service two 9 pin ports.

If handshakes are required, then MAX 232 can only service one port.

In my limited experience, I would say that using one MAX 232 for two ports is unusual, but I see no reason not to.

 

[KeepItSimpleStupid]

A practical minimum interface is TD, RD, SG and DTR, DSR.

DTR and DSR allows stuff to be port powered. RS-232 has been so screwed up from the original specification, so you never knew which was was up.

A way to look at the spec is:
DSR/DTR basically says the device has power
CTS/RTS is basically for hardware handshaking. RTS - can also be looked at as "answer the phone" and CTS - Phone has been answered
RI - the phone is ringing
SG - Signal ground
PG - Protective ground

The RTS/CTS and DSR/DTR functions were not implemented correctly in many devices.

 

[Li Gang]

Many thanks for replies of you two.