I have built an interface to connect an 8052 to a CGA card.
First, I looked for an old CGA card. I was lucky because I found 2 cards. One of them needs the OSC signal. The other one includes an internal oscillator, so that no OSC signal is required. However, it needs a +12 V power supply.
Using the second card (no OSC required) I designed a simple interface including:
1) A MAX662 to obtain +12V from +5V.
2) Two latches (74HCT573).
I connect the P2 port directly to the ISA data bus (CGA), and also to the latches inputs. The latches outputs are conected to the CGA address lines (A0 to A13).
I use the P1 port as a control bus that includes:
RESET
-IOR
-IOW
-MEMR
-MEMW
ADDL_EN
ADDH_EN
The last two are used to control the latches.

In order to access the CGA I/Os or MEM, the program outputs in P2 the address low byte and stores it in one latch. Then, the same action is performed with the high byte in the other latch. Then, the read or write control lines, and the data bus (P1) are used to read/wrire IO or MEM.

My CGA card is not 100% compatible with the 6845 controller, so I could not define some presentation parameters (for example image centering), but it works fine.

So far I have tested text modes only, but I supposse that graphics mode will work too.

I connected the CGA to an old CGA monitor and also to a TV receiver (RCA connector). The quality of the image is poor, I did not realize how much the video adapters and monitors have improved in the last 17 years.

Remember, your specific CGA might need:
* The OSC signal
* A 12V power supply (at least for the video output)
* High current from +5V (more than 0.5 A)

Alfredo del Rio.