The Wiz107SR manual indicates the serial interface is 3.3V RS232. The datasheet for the actual hardware used on the Wiz107SR (a SP3232), indicates the output is “true” RS232 level. In short, can I interface a standard RS232 port with the Wiz107SR serial interface? The chip datasheet indicates I can, but the Wiz107SR manual appears to indicate I can’t.
There are two models of WIZ107SR, WIZ107SR-TTL and WIZ107SR-RS232.
WIZ107SR-RS232 has a RS232 transceiver inside and its voltage level is RS232 level.
WIZ107SR-TTL, however, doesn’t have any transceiver on it. it provides 3.3V TTL level.
You can select the one you prefer.