How much current can a TMS570LS04 GIO pin sink in open drain mode?

Jan,

The values in Table 3.7 are typical digitial logic specs and are all that we have in the datasheet for a DC load.
You get 2 operating points out of this table and usually the device will perform better than these.

These operating points are:

   1) Sink at least IOL while keeping the output voltage at or below VOL(max)  [which is 0.2 * VCCD]

   2) Source at least IOH while keeping the output voltage at or above VOH(min) [which is 0.8*VCCD]

In simpler terms,  take the 8mA output buffers as an example.   This table means that you can drive a '0' out on the pin, and if your external 'pull up' is good for 8mA or less the output voltage will be below 0.2*VCCD.  Let's say VCCD is 3.3V ... than that means the output voltage on the pin will be below 0.66V.

It's probably less than this but you won't find more detailed information as a specification.

We do provide IBIS models that are intended mainly for timing analysis.  However they contain I-V curves in them and if you know how to read the file you can get other points than the above.  It'll take a day or two to wrap your head around these files if it's the first time you use them,  although there are some visualazation tools on the web that can help.   However, you need to be careful on terminology if you take this route,  because what's called 'pull up' in the model is actually the active drive of the output buffer when driving high ... not the strength of what we call a pull up resistor (that's in another table...)