I wrote some software to output programming
info(using SPI: Data,Clock, and Enable) to a MC145158 PLL using a
PIC16F84. Simulated, it works perfectly. On the hardware it works
fine also. But when the chip is finally connected to the device that is to
receive the information, the chip just keeps putting out info
forever.
I am stumped as to why, but here is more info on
the situation. The PLL to be programed operates at around 40MHz. The
oscillator is a mini-circuits POS-75P. The desired product is a radio
frequency synthesizer tunable across 4MHz. The software outputs (MSB
First) the N and A values for the PLL plus a control bit to change the
frequency. On powerup the reference frequency is programmed. The
software is perfect though. The channel is incremented and decremented by
a pair of buttons, but those are active low! Could a weak RF signal cause
the PIC to do that? When the Oscillator was shut down, with the PLL on,
the PIC still kept going. What could be the problem?
Anthony Clay
PICFlyer