Use the email link to contact the author of this page:
http://www.turtlesarehere.com/html/data_logger.html
and he will share his AVR routines which can be easily ported to Microchip assembler.
I didn't really require BASIC code. Assembler source is actually quite abundant.

The routines I have access the SD card as a mass RAM with no FAT system,
which is the same way we use I2C EEPROMS.
Art.