On Friday, November 28, 2014 at 8:08:38 AM UTC-8, Uffe Bærentsen wrote:
Using a voltmeter and an oscilloscope and measure on the pins - that
might help identifying some of the pins.

A Hirose 3540-16P-CV(50) and conductors were assembled to allow
a connection to the port marked RS232 on the Tatung TWN-5213 CU.
https://commons.wikimedia.org/wiki/F...22RS232%22.png

The OS was configured to attempt assigment of four commonly used
(address, IRQ) pairs to COM1 .. COM4.

Addresses & IRQs COM1 COM2 COM3 COM4
{ ConfigV24.SetIRQs 3F8H 4 2F8H 3 3E8H 4 2E8H 3 ~ }
{ ConfigV24.SetIRQs 3F8H 4 2F8H 3 338H 4 238H 3 ~ }
{ ConfigV24.SetIRQs 3F8H 4 2F8H 3 3E8H 4 2E0H 3 ~ }
{ ConfigV24.SetIRQs 3F8H 4 2F8H 3 220H 4 228H 3 ~ }

The machine was booted from the CF card. According to the System.Log,
the assignments to COM1 and COM2 are accepted and the assignments to
COM3 and COM4 fail in all cases.

Invalid address on COM3
Invalid address on COM4
Serial port addr. & IRQs COM1 COM2 COM3 COM4
ConfigV24.SetIRQs 3F8H 4 2F8H 3 000H 0 000H 0 ~
Invalid address on COM3
Invalid address on COM4
Serial port addr. & IRQs COM1 COM2 COM3 COM4
ConfigV24.SetIRQs 3F8H 4 2F8H 3 000H 0 000H 0 ~
Invalid address on COM3
Invalid address on COM4
Serial port addr. & IRQs COM1 COM2 COM3 COM4
ConfigV24.SetIRQs 3F8H 4 2F8H 3 000H 0 000H 0 ~
Invalid address on COM3
Invalid address on COM4
Serial port addr. & IRQs COM1 COM2 COM3 COM4
ConfigV24.SetIRQs 3F8H 4 2F8H 3 000H 0 000H 0 ~

If a Logitech serial mouse driver is assigned to COM1 and the system
boot trace is assigned to COM2, the mouse pointer moves erratically
when the screen is touched. The scope shows no signal on any pin of
the Hirose connector.

If the boot trace is assigned to COM1 and the Logitech serial mouse
driver is assigned to COM2, the mouse pointer is unresponsive when
the screen is touched. Again the scope shows no signal on any pin
of the Hirose connector.

My conclusion from these observations is that COM1 is connected to the
touchscreen. COM2 appears to be present but non-functional. COM3 and
COM4 do not exist in the machine or they exist and are disabled by the
BIOS. Further progress appears to require information about the hardware
or access to the BIOS.

Comments welcome.

Thanks, ... Peter E.