Re: [ECOS] MPC860 and IMMR location

[Gary Thomas <gary@chez-thomas.org>]

On Thu, 2002-07-18 at 09:54, Barton Meeks wrote:
> As I stared writing this, I was thinking there was a
> problem with the viper HAL, but it may just be a
> matter of me being confused by the comments.  In the
> code below, I believe 0xff000000 is indeed the MCP
> registers for just a brief period, until viper.S gets
> going.  Then the internal memory is moved to
> 0xfa020000, which is listed in the comments below as
> "Control/Status+LEDs."
> 

The comments are stale, sorry.  In fact, I don't think the
0xFF000000 space is used anymore at all.

The MCP registers were moved to 0xFA020000 to be more compatible
with the Motorola MBX series of boards.

> This is from viper/current/src/hal_aux.c:
> 
> CYGARC_MEMDESC_TABLE CYGBLD_ATTRIB_WEAK = {
>     // Mapping for the Viper 855/860 development
> boards
>     CYGARC_MEMDESC_CACHE(   0xfe000000, 0x00800000 ),
> // ROM region
>     CYGARC_MEMDESC_NOCACHE( 0xff000000, 0x00100000 ),
> // MCP registers
>     CYGARC_MEMDESC_NOCACHE( 0xfa000000, 0x00400000 ),
> // Control/Status+LEDs
>     CYGARC_MEMDESC_CACHE(   CYGMEM_REGION_ram,
> CYGMEM_REGION_ram_SIZE ), // Main memory
> 
>     CYGARC_MEMDESC_TABLE_END
> };
> 
> 
> 
> 
> Background information:
> 
> At reset time, the 860 family has a configuration (via
> device pins) as to the location of the internal memory
> space. This controls the initialization of the IMMR
> register, which can be later changed by software.
> 
> This setting of the IMMR is changed by ecos based on
> the setting here:
> 
> mpc8xx/current/include/var_regs.h:
>     #define CYGARC_REG_IMM_BASE 0xfa200000
> 
> I'm guessing that the initial (at reset) value doesn't
> really matter, since the value listed above is written
> to the IMMR first thing in hal_hardware_init (such as
> in the files mbx.S or viper.S.)
> 
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