Structures and XMEM

Rabbit
1

Does anyone have an example of reading and writing a structure in XMEM?
I need to place a 7000-byte structure ( a mix of chars and int) and can’t work out how to write and read them using normal structure access

2

What processor? IIRC, on the 4000 and 5000 you can just access the data directly, while on earlier ones you need to use xmem2root()…

3

Hi,
I am using the RCM4010.
My structure is like
typedef struct {char Model;
char Active;
char MixerID;
int Reading[10];
} METER_DATA;

gldef_d METER_DATA Mixer;

so I amhoping to use lines like
a = Mixer.Reading[4];
and Mixer.Redaing[0] = 0xFF;

4

What is gldef_d defined to be? If it’s far, you should be OK.

5

Hi,
actually it is declared as follows

#define GLDEF_C
#define GLREF_C extern
#define GLDEF_D
#define GLREF_D extern
#define LOCAL_C extern
#define LOCAL_D

I have spotted the use of this
#memmap xmem

I have tried adding far to the #define but i still get the same problem… “out of variable space”. I am only declaring around 15-20K of data so am puzzled as to why I am having this problem.

6

In Dynamic C�s Main menu, you should open Options -> Project Options-> Compiler.

Select �Use separate Instruction and Data Space�
Select �Optimize for Size�

See if that makes any difference for you.

Also see Tech Note 238 located at http://www.rabbit.com/documentation/docs/refs/TN238/TN238.pdf

Also try changing
char Active;
char MixerID;
to
auto char Active;
auto char MixerID;

7

Hi,

Thanks for that. I had actually tried that yesterday and it did fix my initial problem.
I realise afterwards (and having done a bit more reading) that I was incorrectly thinking that I had direct access to effectively most of the 512K RAM so was surprised that after only about 30K of declarations that I was getting memory space problems. I see that I only have, initially, access to space in a 64K page and that other mechanisms are needed to access the rest of memory.

Although not a concern at the moment for the current project I do need clarification on how to cleanly store/access data in other pages - I will need to store data of various types and structures in the order of 100K and don’t see how to do this easily…