Chip = 16F1829
Ceramic resonator: muRata (source: DigiKey), 8 MHz
PCB = soldered breadboard FR4
Problem: In HS mode (datasheet specifies that mode for 4 MHz to 20 MHz), frequency is 0.3% high. Still within spec, but would like to pull it lower. Rock stable for frequency. In XT mode, frequency is better, but not as stable.
Attached an EZ micrograbber to one leg (OSC1/CLKIN) and frequency got better. The datasheet shows some external resistors:
Space is very limited, so any modifications take more time, even just swapping resonators. I am wondering whether it is being over-driven. Question: Can RP and/or Rs be used to pull the frequency down?
Other suggestions?
John
BTW: Curious bit in the errata: The OSTS status bit remains clear when using 4XPLL through version 4. Problem was easily discovered. I guess I wasn't the first to find out.
Ceramic resonator: muRata (source: DigiKey), 8 MHz
PCB = soldered breadboard FR4
Problem: In HS mode (datasheet specifies that mode for 4 MHz to 20 MHz), frequency is 0.3% high. Still within spec, but would like to pull it lower. Rock stable for frequency. In XT mode, frequency is better, but not as stable.
Attached an EZ micrograbber to one leg (OSC1/CLKIN) and frequency got better. The datasheet shows some external resistors:
Space is very limited, so any modifications take more time, even just swapping resonators. I am wondering whether it is being over-driven. Question: Can RP and/or Rs be used to pull the frequency down?
Other suggestions?
John
BTW: Curious bit in the errata: The OSTS status bit remains clear when using 4XPLL through version 4. Problem was easily discovered. I guess I wasn't the first to find out.