I have posted two Si570-related files (in the *W7QJQ folder). One is a program to read and display (on an acsii terminal) the factory-programmmed Start-Up parameters including N1, HS_DIV, RFREQ, and the internal xtal frequency.
The other, a bare-bones routine to input (from the keyboard) a frequency in the range of 3.5 MHz to around 1300 MHz, select the correct Si570 divisors, and DCO tuning word, and load a frequency into a Si570 chip. Both are programmed in BASCOM, a VB-like language molded closely the Atmel AVR series of uC's. See the file folder for more details on the programs, a few metrics related to floating-point math and speed, as well as the source code. 73, Sid W7QJQ Oklahoma
