Make crt0 use a configuration that is likely to work well with many programs about openrabbit HOT 5 CLOSED

In general, the generic crt0 approach is apparently working, but there are still issues:
Dhrstone doesn't complete its output:

Enum_Loc:            1
        should be:   1
Str_1_Loc:           DHRYSTONE PROGRAM, 1'ST STRING
        should be:   DHRYSTONE PROGRAM, 1'ST STRING
Str_2_Loc:           DHRYSTONE PROGRAM, 2'ND STRING

Output ends here, so there are a few lines missing (including the final score). Also, at startup, the line

Dhrystone Benchmark, Version 2.1 (Language: C)

Is shown twice, as if the program restarts in the middle of execution. Maybe there is some issue with how we setup the clock doubler or other configration, that makes the Rabbit unstable?

P.S.: Even without the clock doubler, and with MB0CR and GCSR at reset value and MB2CR at the "safe" value from the generic crt0, I still see the same problem. At least that means that the problem is not the watchdog - the watchdog one is timed from a separate clock, so we'd get a noticeable change in behaviour when running Dhrystone much slower.

P.P.S.: I found the problem: I forgot to update the Makefile with the correct value for --data-loc. With this fixed, Dhrystone works.

from openrabbit.

I've read through the documentation of 7 RCM now.
All of them have:

• Flash at /CS0, /OE0
• RAM at /CS1, /OE1, /WE1

This is also what coldload.bin assumes (which gets these values from the default makecold configuration).

We might not necessarily get the fastest configuration from that (RCM3209 has additional faster RAM at /CS2), but something that works on nearly all hardware.

For Flash, we could just leave MB0CR in its reset state. For RAM, I suggest to configure on of the other MBxCR registers to 0x05.
Due to backwards-compability in the Rabbit 4000 MMU, the generic crt0 should even work with the RCM for Rabbit 4000.

from openrabbit.

A first version of such a generic crt0 is now in the repo as crt0-generic.s. It works for me on the RCM2200.

from openrabbit.

I'll try to do a bit more testing with the generic crt0 next week, then, assuming no problems turn up, merge it into SDCC.

from openrabbit.

The current generic crt0 works with at least 6 different boards (i.e. all the boards I have).

from openrabbit.