Inspiron 5000 RS232 port behavior

Archived from groups: alt.sys.pc-clone.dell (More info?)

We have some boot loader software which fails on some Dell notebook
models ( inspiron 5000, 8000 ) and works fine on other ( latitude D600
).
When measuring the PC COM port TX pin ( output ) signal level it is
not - 3..12 V as expected, but + 5V, when there in no activity on the
port. When a program transmit data the TX pin switch to -5V before
start of the first byte, and data is transmitted. Approx 300 ms after
last byte is transmitted the TX pin switch from - 5V to + 5V again.
The port work and is apparent not damaged.

Is this a known Dell 'feature', and is there a work around ?

The actual problem is the connected device is in autobaud mode,
waiting for a known char to calculate the baudrate, which fail.





Regards

Geert Petersen

gp_AT_BrodersenControls_DOT_com