XCAPxPF Configuration

Benjamin Lippi said:

I've found on XCAPxPF indicates its only 2 bits

Indeed. There are only four different values available, one of them being the plain pin capacitance.
On different MSP families, teh available values change a bit. So the available convenience defines XCAPxPF are different.
Basically, you must set bit 4 and 5 according to the desired configuration, as shown in the datasheet. No magic there.

Thanks for the response, unfortunately I didn't convey what exactly was I was having trouble with. Sorry about that.

What confused me is that for basically every other registers I would set a value of lets say '3' (11b) by putting in "XCAP3PF". For this the example code lists it as "XCAP14PF" which is well outside the range of 0-3 and doesn't match up with bits 4 and 5 either, 14 = 1110b

You're right with this. This bit naming is somewhat special.

usually, the bitfield is named something liek XCAPx (with x being 0 or 1 for a two-bit field).
Then there is a define XCAP0 and XCAP1, and also an enumeration define XCAP_0, XCAP_1...XCAP_3. And often there are the 'convenience defines' named XCAP_1PF, XCAP_10PF etc. Or, if the function of this bit ocmbination is a plain number, it is named XCAP__1 (double-underscore).

But for some unknown reason, someone decided to name these bits in the 4x family "XCAPxPF", so these completely unusual defines exist. (on 1x family, XCPA is not programmable, and on 2x and 5x family, the bits are named XCAPx)

It's still possible that someone else still defined XCAP0/XCAP1 and XCAP_0..XCAP_3  or maybe XCAPxPF_0..3. Maybe you can check your header files.

I suspected it was something like that, but the part that was throwing me off was the "4", which would be outside the 0-3 range.

I checked the header files after you mentioned it and found this:

#define XCAP0PF             (0x00)                     /* XIN Cap = XOUT Cap = 0pf */ #define XCAP10PF            (0x10)                     /* XIN Cap = XOUT Cap = 10pf */ #define XCAP14PF            (0x20)                     /* XIN Cap = XOUT Cap = 14pf */ #define XCAP18PF            (0x30)                     /* XIN Cap = XOUT Cap = 18pf */

From there it looks like its just some legacy code thats causing confusion. Basically it just needs to be matched up to the appropriate value listed in the user guide. So if my guide says:

XCAPxPF Bits 5−4 Oscillator capacitor selection. These bits select the effective capacitance seen by the LFXT1 crystal or resonator. Should be set to 00 if the high-frequency mode is selected for LFXT1 with XTS_FLL = 1. 00 ~1 pF 01 ~6 pF 10 ~8 pF 11 ~10 pF

And I wanted 6 pF. I would use "XCAP10PF".

Thanks for your help. Hopefully this will help anyone else that runs into this problem.

Benjamin Lippi said:

And I wanted 6 pF. I would use "XCAP10PF".

Not exactly. It should be something like XCAP1PF (and XCAP0PF) for the individual bit 5 (and 4), XCAP_0PF..XCAP_3PF for the enumeration of the four options or XCAP__0PF, XCAP__6PF etc. for the 'meaning'.
Whoever created the header fiels was obviously confused by the 'x' not being the trailing part of the field name, as it is for all other fields in the MSP430 universe.
AFAIK this is the only severe inconsistency. And has been fixed on 5x family.