Getting Lenovo T500 ECP Parallel Port and Serial Port to Coexist

Topics related to the Dataman 48, 48LV, 48XP and 48UXP
Billy Crowson
Posts: 2
Joined: 07 Feb 2021 03:45

Getting Lenovo T500 ECP Parallel Port and Serial Port to Coexist

Postby Billy Crowson » 07 Feb 2021 04:59

Posting this for whomever might find it helpful later on.

** Short Version **

On the Lenovo ThinkPad T500 (and probably similar laptops), a ECP parallel port, serial port, and PCI power management do not play well together. One of them has to be eliminated, at least in a Windows 7 environment anyway.

** Full Story **

In September 2020 I installed the Dataman 48UXP software on a Lenovo ThinkPad T500 laptop running Windows 7. The T500 is docked in a ThinkPad Advanced Mini Dock. The 48UXP connects to the parallel port of the Mini Dock.

When I installed the software, I had to configure the parallel port in BIOS as "ECP" (though I understand "EPP" may have worked as well). The parallel port is configured as LPT1 using the default addresses, IRQ, and DMA.

The serial port of the Mini Dock is used to program my home automation system. The serial port is configured as COM1 using the default addresses and IRQ. I sometimes go 6 months or more without needing to connect to the home automation system. This past week (February 2021) I needed to do some programming on my automation system and discovered that the serial port was not working.

I have extensively tested and, using a second T500, verified the following information.
When the parallel port is set to "ECP" in BIOS, the serial port becomes unstable. There will be brief, random periods where the serial port will transmit and receive correctly, but mostly the port is non-responsive.

When the parallel port is set to "EPP" or "Bi-directional" or "Transmit Only" in BIOS, the serial port is unaffected. But of course, the 48UXP specifically requires "ECP" or "EPP".

Because I had a working installation of the 48UXP on the parallel port in ECP mode, I wanted to find a way to continue using the "ECP" setting in BIOS. In the T500 BIOS I discoved that if I changed the "PCI BUS POWER MANAGEMENT" setting to "DISABLED" instead of the default "AUTOMATIC", the problem with the serial port disappeared. This setting can be found under "CONFIG" >> "POWER" >> "PCI BUS POWER MANAGEMENT".

I wanted to dig into the issue further to understand why this was happening but found that there is scant technical information on the BIOS, the T500, the Mini-Dock, etc. I'll just have to be satisfied that I found a way to keep this old tech working together.

Billy

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