Post by thread:[PIC]MPLAB ASM30 variable question

I am currently reading the documentation for MPLAB ASM30 and will be writing code for the dsPIC30F2010. When coding for non-dsPIC devices, CBLOCK is used to declare relocatable variables. I do not see how this is done for the dsPIC.Either I have spent too much time reading and cannot see the obvious, or I really am missing something. Can anyone point me in the right direction? -- Regards, Stephen D. Barnes

Stephen D. Barnes wrote : > When coding for non-dsPIC devices, CBLOCK is used to > declare relocatable variables. Don't use CBLOCK för *any* PICs. That will make life easier, in particular when switching to PIC24/30/33, since CBLOCK, as far as I know, isn't supported when developing for them (or any other absolute-mode-specific directives). That is a good thing, imho. > I do not see how this is done for the dsPIC. How *what* is done ? Allocating RAM space ? You should read about RES. > Can anyone point me in the right > direction? =======>>> ***Relocatable code*** B.t.w, doesn't the docs have some chapter named "Allocating RAM" or something like that ? Best Regards, Jan-Erik.

Stephen First of all, CBLOCk is not "used to declare relocatable variables". CBLOCK simply assigns a string of sequential constants. In absolute programming (as opposed to relocatable programming) CBLOCK might be used to assign a string of constants which refer to fole register locations, bt they are not relocatable, and they are not "variables". They are simply constants that contain values that happen to correspond to GPR locations that you have chosen to use for variable storage. In the PIC16x/18x look at udata and res for relocatable gpr allocation. On the dsPIC look at .bss for a similar capability. --McD

Stephen D. Barnes wrote: > When coding for non-dsPIC devices, CBLOCK is used to > declare relocatable variables. Argh! After the many discussions on this I thought everyone got this by now. CBLOCK does not allocate variables, and it certainly isn't used to declare variables in relocatable mode. All CBLOCK does is create a bunch of symbols with sequential values. This is used in ancient crufty absolute code to define variable symbols, although this has associated problems. CBLOCK should only be used for something simular to a C ENUM. Variables are defined and allocated with the RES directive. > I do not see how this is done for the dsPIC. What, defining symbols with sequential values or defining variables? The latter can be done several ways, including with the .BSS directive. I use a macro called ALLOC to get more flexibility about what section the variable goes in, but you can start out using .BSS. ****************************************************************** Embed Inc, Littleton Massachusetts, (978) 742-9014. #1 PIC consultant in 2004 program year. http://www.embedinc.com/products

Jan-Erik Soderholm wrote: > Allocating RAM space ? > > You should read about RES. The OP was asking about dsPICs, which have a totally different assembler and linker. There is no such thing as absolute mode on dsPICs, for example. The directives are also different and there is no RES directive, although there are ways of achieving the same thing. ****************************************************************** Embed Inc, Littleton Massachusetts, (978) 742-9014. #1 PIC consultant in 2004 program year. http://www.embedinc.com/products

Olin Lathrop wrote : > Jan-Erik Soderholm wrote: > > Allocating RAM space ? > > > > You should read about RES. > > The directives are also different and there is no RES > directive,... Yes, I saw that from later post, I thought about posting a correction, but hoped that the OP would sort it out using the info in the later posts... Sorry about that. Jan-Erik.

Olin Lathrop wrote: >Stephen D. Barnes wrote: > > >>When coding for non-dsPIC devices, CBLOCK is used to >> >> >> >declare relocatable variables. >Argh! After the many discussions on this I thought everyone got this by >now. > > > > Sorry Olin! I should have mentioned that I have been away from PIC's altogether for almost a year and have been intermittent at best in my reading the PICList. I was a beginner at the time I accepted a field engineering position that required 90% travel. I am now In one location with somewhat normal hours at work and at home. I do appreciate the reply and it has led me in the right direction. Thank you for the help! -- Regards, Stephen D. Barnes

Thanks to everyone for the input. I am on the right track now. For those interested, I am attempting to implement a dedicated brush DC servomotor controller...yes... for hobby robotics. The dsPIC30F2010 has a hardware QEI which maked the design a bit easier for me. -- Regards, Stephen D. Barnes