FNX6809 Manuals: Difference between revisions
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<nowiki>*</nowiki> system powers off. | <nowiki>*</nowiki> system powers off. | ||
'''NOTE:''' If you are writing an | '''NOTE:''' If you are writing an OS-9 program, use <code>F$MapBlk</code> and <code>F$ClrBlk</code> instead of directly accessing these addresses. NitrOS-9 keeps track of each process' MMU LUT (but only if you use <code>F$MapBlk</code> and <code>F$ClrBlk</code>). Addressing the MMU directly can create unpredictable results. | ||
== Memory Map == | == Memory Map == | ||
[[File:K2MemoryMap.png|frameless|818x818px]] | |||
== Memory Model == | == Memory Model == | ||
[[File:FNX6809-MemoryModel Page 1.png|thumb|430x430px|FNX6809 Memory Model Page 1|none]] | |||
[[File:FNX6809-MemoryModel Page 2.png|none|thumb|430x430px|FNX6809 Memory Model Page 2]] | |||
__FORCETOC__ | |||
Latest revision as of 08:19, 29 August 2025
MMU Registers
| Address | R/W | Name | 7 | 6 | 5 | 4 | 3 | 2 | 1 | 0 |
|---|---|---|---|---|---|---|---|---|---|---|
| $FFA0 | RW | MMU_MEM_CTRL | - | - | EDIT_LUT | - | - | ACT_LUT | ||
| $FFA1 | RW | MMU_IO_CTRL | - | - | - | - | - | $FFF0-$FFFF
Enable |
$FD00-$FDFF
Enable | |
There are 4 MLUTs (MMU Lookup Tables).
ACT_LUT these two bits specify which MLUT (0–3) is used to translate CPU bus address to system bus addresses.
EDIT_LUT these two bits will specify which MLUT (0 - 3) is being edited and will appear in memory addresses $FFA8-$FFAF.
These locations are defined in nitros9/defs/f256.d:
MMU_MEM_CTRL equ $FFA0
MMU_IO_CTRL equ $FFA1
MMU_SLOT_0 equ $FFA8 $0000-$1FFF
MMU_SLOT_1 equ $FFA9 $2000-$3FFF
MMU_SLOT_2 equ $FFAA $4000-$5FFF
MMU_SLOT_3 equ $FFAB $6000-$7FFF
MMU_SLOT_4 equ $FFAC $8000-$9FFF
MMU_SLOT_5 equ $FFAD $A000-$BFFF
MMU_SLOT_6 equ $FFAE $C000-$DFFF
MMU_SLOT_7 equ $FFAF $E000-$FFFF
* MMU_IO_CTRL bits
* $FFA1 has 2 bits:
* FFA1[0] =
* 1 = Enable internal RAM for segment $FD00-$FDFF.
* 0 = Disable; RAM/FLASH is accessible.
*
* FFA1[1] =
* 1 = Enable internal RAM for segment $FFF0-$FFFF
* 0 = Disable; RAM/FLASH is accessible.
* When enabled, the areas supersede RAM/flash, but will be disabled by RESET. When the system resets,
* those regions revert to RAM/flash. Also at RESET, the contents of RAM retain the old values until the
* system powers off.
NOTE: If you are writing an OS-9 program, use F$MapBlk and F$ClrBlk instead of directly accessing these addresses. NitrOS-9 keeps track of each process' MMU LUT (but only if you use F$MapBlk and F$ClrBlk). Addressing the MMU directly can create unpredictable results.
Memory Map
Memory Model
