Just plugged it into PC's COM1, opened TeraTerm, set serial port at 4800/8N1, waited for about one minute and watched the strings including $GPRMC. Then I wrote 8051 asm code to wait for '$' beginning of new string, grab the string, reject anything else than $GPRMC, extract time, position and date fields, then convert ASCII to packed BCD and store date/time into a M48T02 Timekeeper SRAM (as my SBC has additional UART, it is easy to echo those fields to the main terminal running at 57600 bps). To do: discard strings without 'A' status, wait several days, compute clock drift and set calibration. Could do it and place in Code Library if someone else is interested.