alternative communication programing a 504

What's the best and least expensive form of (programing)communication if my rs232 port is being by a red lion HMI, all other plc's that we are using (504's) are configured with using DH+ or for local RS232, I would rather not put it on the DH.

regards,
Mark

I am assuming that the RedLion is using DF1 protocol.

In that case you may be able to use an RS232 port splitter/mux such as: Tomantron

If I have understood this device correctly it will allow your HMI and RSLinx DF1 driver to BOTH access the 5/04 Ch0 port at the same time. Cool eh!

I can second a recommendation for the tomantron. Great little black box!! The maker also posts here regularly.