well, I have used the ds1302 in a data logger based on the 628 (2K code) my entire program is is about 1.25K but the biggest chunk of the code deals with reading the time and date from the serial port and formatting up the date and time for sending to the serial port. The SPI and ds1302 code occupies about 120 code words (set time, get time, set date, get date, init, spi functions). Written in C using CC5X. I'm sure I could shoehorn this into 1K if I removed a bunch of error checking on the date/time input and cleaned up the code a bit. Certainly in ASM it could fit in 1K.
more details are needed. I'm pretty sure this is surmountable without moving to a bigger chip.
Phil