[Simulavr-devel] Output Compare registers.

[Keith Gudger]

Ted:

Here is what's going on with the Output Compare Registers.  It will also
affect Input Capture registers, whenever that code exists.

The Timer16 structure has the following members:
    OCReg16_T *ocra;            /* Output compare registers */
    OCReg16_T *ocrb;            /* Output compare registers */
    OCReg16_T *ocrc;            /* Output compare registers */

These pointers are used by the Timer16 clock routine to decide when to set
the OCRx interrupt flags in the TIFR register.  This register was passed
to the timerxx_create() functions in the .related field.

The OCReg's get created before the Timers (because their addresses are
smaller) by calling ocreg16_create.

Currently the pointers above *do not* get filled with the proper value.
As far as I can see, they never were.  That means the clock callback can't
find them and the interrupts can't get set.

With the current order in the 43usb3xx.h files, there are no fields left
to pass the OCReg addresses to the timerxx_creates (and there would need
to be at least 3 fields).  Here is one suggestion on how to do this:

1.  Timer creates come first in the file.
2.  OCReg creates use .related to point to the associated timer.
3.  OCReg create finds the Timer with avr_core_get_vdev_by_addr(), and
installs a pointer to itself in the appropriate place.

Problems with this include that the OCReg create might not know which one
it is (a,b,c?) and that the OCReg creates come out of numerical sequence.

All of this code is in the timers.h/c that I started with, so you don't
need to look at the updated code to find this.

Suggestions?  Or is my rambling unintelligible?  Would you prefer that the
.data field passed to the timerxx_create be an array with OCReg info in it
(as another way to do this)?

Keith