TRAP and BKPT details

[Gravis]

ok, so the BKPT and TRAP instructions have just about no information on how they work in the Epiphany Architecture Reference because they are not intended to be used by users directly. since i'm writing an emulator, i could really use detailed information about them. it seems like there will be lots of information to compile to clearly explain it (seems like there are protocols involved), so i can wait if you need time to organize it. btw, the "Operation" sections are the most helpful part of the arch documentation (for me). these are the last instructions of the instruction set that i need to implement. now to work on the DMA stuff.

[EggBaconAndSpam]

"The TRAP instruction causes the processor to halt and wait for external inputs."
- is "external interrupt" used to describe any interrupt? If not, please define the applicable subset...

Other than that, I am quite certain that the epiphany architecture does not guarantee any timings on TRAPs, they are to be interpreted by the host device (the almight ARM in the case of Parallella, potentially the FPGA interferes to some degree).
Anyway, the interpretation of TRAPs is out of spec for the chip, you should either treat them as breakpoints, or expose some sort of API to handle them.

Even though the Mighy Book of Reference mentions TRAP 7 in context with file handling syscalls, a look at the current epiphany-libs, implies that they are yet to be implemented. Treating TRAPs as breakpoints (or runtime exceptions, if you so desire) should therefore be compatible to the current setup.

As for the BKPT: similar situation...

All in all, mimicking a certain debugger's behaviour (in this case GDB) does not seem necessary at emulation level (real code does not depend on the way breakpoints are interpreted, and TRAPs aren't implemented yet, anyway), feel free to expose breakpoints and TRAPs through a custom API...

Or just crash, you know... (Though not mentioning the TRAP parameter does seem unnecessarily cruel to me)

[aolofsson]

[Gravis]

[tnt]

@Gravis: btw, it would be great if you could plug your emulator as a 'device' in qemu. Curently qemu can emulate the zynq and some of it's peripherals (like usb / sd / gpio / ...) and if it could emulate the epiphany as a device as well we'd have a complete system emulator.

[9600]

[Gravis]

[ysapir]

[tnt]

[Gravis]