The LM238B has an HD61830 controller onboard. My LM213XB is an updated LCD, but the controller works the same, so I would guess the "X" is just an updated LCD on yours also.
Google the HD61830 and the first hit is
formatting link
which tells you more than you want to know about it, but it does have the
programming info.
The 10 pin is not to be used! The 20 pin is labeled A1-A20 and on my picture is just pads with the A1 on the left side of the front view.
A1-VSS- Ground A2 VDD-(+5V) A3-Vo-LCD power A4-RS-Register select A5-R/W-Read/Write A6-E-Enable A7-14 DB0-DB7 Data bus A15-CS-ChipSelect(active low) A16-RES-Reset(active low) A17-VEE-(-13.5V) A18-20 N.C.
The sample for LCD bias is a pot connected to VDD and VEE with the wiper connected to Vo.
A source for the VEE could be tapping the -12V on a Maxim 232 chip with a
larger cap in the -V charge pump, which is what I did on my LCD terminal:
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