You do it at your own risk ! You may fry your pic (cheap) and/or your si570 (not cheap).

XTALL Si570 - 12F683 HEX eeprom file modification

For Firmware 2.4 here

XTALL Si570 - 12F509 dipswitch pic ASM

For Experiments in ASM here

XTALL Si570 - 12F509 RS232 control

Psdr control is bottom of page here

XTALL Si570 - 12F683 RS232 control

Powersdr control for the XTALL here