 | | RE: signals / legOS internals
|
|
(...) Not to put too fine a point on it, and I hope Kekoa agrees, but the "fluff" is the reason why replacement firmware works in the first place. Without the ROM vectors being dispatched through RAM pointers that are initialized by the ROM and then (...) (25 years ago, 23-Jun-99, to lugnet.robotics.rcx.legos)
|
| |
| | Re: signals / legOS internals
|
|
(...) Since it sounds like it might matter to you, I should point out that the interrupt situation on the RCX is a bit more complicated than the H8 manual makes it out to be. Interrupt vectors are in ROM, but the ROM does a dispatch to interrupt (...) (25 years ago, 23-Jun-99, to lugnet.robotics.rcx.legos)
|
| |
| | Re: signals / legOS internals
|
|
(...) Yes, that is correct. As for passing parameters to a function, they are simply pushed onto the stack before the function call. Therefore, the H8 stack usually looks something like e.g. this: function param sp+10 function param sp+8 return (...) (25 years ago, 23-Jun-99, to lugnet.robotics.rcx.legos)
|
| |
| | Re: signals / legOS internals
|
|
(...) I may have answered my own question here. Since the SP is adjusted before anything is actually done with the local variables, the rule about it always pointing to the last valid datum is not violated even if local variables are placed after (...) (25 years ago, 23-Jun-99, to lugnet.robotics.rcx.legos)
|
| |
| | Re: signals / legOS internals
|
|
(...) I may have down and up reversed, since different machines grow the stack upward or downward, and I've worked with a few. I do have push and pop clear in my mind, though. So, yeah, down. So, by the "always" rule, nothing will ever be below the (...) (25 years ago, 23-Jun-99, to lugnet.robotics.rcx.legos)
|
| |
| | Re: signals / legOS internals
|
|
(...) When you define a bunch of local variables (more than fit in available registers), where are they? Unless you happen to know the answer, I may have to do some more experimenting. Admittedly, it has been awhile, but the last time I was heavy (...) (25 years ago, 23-Jun-99, to lugnet.robotics.rcx.legos)
|
| |
| | Re: signals / legOS internals
|
|
(...) Reading this again, I should mention that pushing things on the stack asynchronously is fine, as long as the stack pointer is always in the right place, which is why it must always always always point to the location I mentioned (and seemingly (...) (25 years ago, 23-Jun-99, to lugnet.robotics.rcx.legos)
|
| |
| | Re: signals / legOS internals
|
|
(...) The stack pointer must always always always point at the bottom of the stack data area, i.e. to the last valid data item on the stack. As a consequence, push val (or mov.w val,@-r7) never overwrites data. When an interrupt occurs, the first (...) (25 years ago, 23-Jun-99, to lugnet.robotics.rcx.legos)
|
| |
| | signals / legOS internals
|
|
Peek-a-boo! I've been banging my head against this a bit and thought I'd see if any of you can shove me in the right direction. I am trying to implement signals in legOS. The problem is that a signal can happen at any time. I know how to make that (...) (25 years ago, 23-Jun-99, to lugnet.robotics.rcx.legos)
|
| |
| | Re: IR questions
|
|
(...) Only transmitting keeps the tower alive, at least according to my tests. If absolutely necessary, an occasional 0xff sent by the PC will keep the tower alive; this will result in only a start bit being sent, which ought to occupy very little (...) (25 years ago, 22-Jun-99, to lugnet.robotics.rcx.legos, lugnet.robotics)
|
