S12 / MagniV Microcontrollers中的主题 Re: Read-Only, I said!

Read-Only, I said!

WadeH — Thu, 29 Oct 2020 09:37:27 GMT

I have a program with the following two sets of data:

  // a list of ADDRESSES of BYTEs
#pragma INTO_ROM
  const  byte * These_Data[]={
&P12.b.high,          &P12.b.low,
&N12.b.high,          &N12.b.low,  
&HVDC.b.high,         &HVDC.b.low,
......
     };
#pragma INTO_ROM
// a list of LITERAL BYTEs
const byte These_Codes[] ={
P12_HB,         P12_LB,    
N12_HB,         N12_LB,  
HVDC_HB,        HVDC_LB,
......
     };

The first is a list of addresses of data in SRAM... some words, some bytes, some longs, but all addressed as bytes

The second is a list of literal byte-values that will be sent along with the data found at the associated addresses.

No matter what I do, the LITERALS are compiled into ROM and the ADDRESSES end up in SRAM.

I'm not (yet) hurting for space, but it bugs me that data that is obviously (to me) invariant is always put in R/W memory.

What am I missing?

(9S12DX256, CW 5.90)

Thanks for any illumination

Wade Hassler

Re: Read-Only, I said!

pgo — Thu, 29 Oct 2020 09:37:29 GMT

Dear Wade,

Try adding a second const . All you've done so far is say that the things pointed AT are constant - not the array itself.

#pragma INTO_ROM  const  byte * const These_Data[]={&P12.b.high,          &P12.b.low,&N12.b.high,          &N12.b.low,   &HVDC.b.high,         &HVDC.b.low,......     };

You didn't say what target but a similar example worked on CFV1 (Eclipse)

bye

Re: Read-Only, I said!

pgo — Sat, 26 Feb 2011 11:28:01 GMT

Actually - you did say what chip - I just didn't read

bye

Re: Read-Only, I said!

kef — Sat, 26 Feb 2011 14:06:21 GMT

const char * const x; // const pointer to const data

const char * x; // nonconst pointer to const data

char * const x; // const pointer to nonconst data

Re: Read-Only, I said!

WadeH — Tue, 01 Mar 2011 07:46:03 GMT

Just so. Thank you for the help and the cheat-sheet

Wade Hassler