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Memory Management
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The F256 line comes with 512 KB of RAM and 512 KB of flash memory. Up to 256 KB additional Memory, either RAM or Flash, can be added through the [[Expansion Port]]. === Physical Memory Layout === The address bus is 21 bits wide, allowing a total of 2<sup>21</sup> = 2 MB to be addressed. {| class="wikitable" !Address!!Purpose |- |$00:0000 - $07:FFFF||RAM |- |$08:0000 - $0F:FFFF||Flash |- |$10:0000 - $13:FFFF||Expansion Memory |- |$14:0000 - $1F:FFFF||Reserved |} === Memory Management Unit (MMU) === While the address bus is generally 21 bits wide, the CPU address bus of the 65c02 and the FNX6809 is only 16 bits wide. Even though the 65816 does have a 24 bit wide address bus, it is currently not used. However, this might change with a future update. To allow the addressing of the whole address space, 4 Memory Management Units (MMU) are provided, that translate the CPU logical address space to physical addresses. To achieve this, each MMU has 8 <em>slots</em>, each representing an 8 KB block of the CPU addressable memory space. The physical address space is also divided into 8 KB blocks, dividing the available 2 MB into 256 blocks. To <em>map</em> a block of physical addresses into CPU address space, the block number is written into the according slot register of the MMU. {| class="wikitable" !Slot!!CPU Address Space!!Slot Register Address |- |0||$0000 - $1FFF|| $0008 |- |1||$2000 - $3FFF|| $0009 |- |2||$4000 - $5FFF|| $000A |- |3||$6000 - $7FFF|| $000B |- |4||$8000 - $9FFF|| $000C |- |5||$A000 - $BFFF|| $000D |- |6||$C000 - $DFFF|| $000E |- |7||$E000 - $FFFF|| $000F |} Only one MMU is active at any one time. To select the active MMU, the lower two bits of address $0000 (MMU_MEM_CTRL) are used. Editing of MMUs is also controlled by MMU_MEM_CTRL ($0000): Bits 4 and 5 determine which set of MMU registers is to be edited, while bit 7 has to be set to 1 to enable editing. When editing is enable, the block number of a physical memory area can be written to the slot register address to map that area to the address in CPU address space. If editing is not enabled (bit 7 of $0000 is 0), the slot register addresses act as ordinary memory with no side effect. === Memory Block Tables === The following table shows which block number has to be written into a slot register to make the each 8 KB block of memory available to the CPU. {| class="wikitable" style="border: none; background: none;" ! colspan=2 scope=col| RAM | rowspan=66 style="border: none; background: none;" | ! colspan=2 scope=col| Flash | rowspan=66 style="border: none; background: none;" | ! colspan=2 scope=col| Expansion |- ! scope=col | Block Number ! scope=col | Physical Address ! scope=col | Block Number ! scope=col | Physical Address ! scope=col | Block Number ! scope=col | Physical Address |- |$00||$00:0000 - $00:1FFF||$40||$08:0000 - $08:1FFF||$80||$10:0000 - $10:1FFF |- |$01||$00:2000 - $00:3FFF||$41||$08:2000 - $08:3FFF||$81||$10:2000 - $10:3FFF |- |$02||$00:4000 - $00:5FFF||$42||$08:4000 - $08:5FFF||$82||$10:4000 - $10:5FFF |- |$03||$00:6000 - $00:7FFF||$43||$08:6000 - $08:7FFF||$83||$10:6000 - $10:7FFF |- |$04||$00:8000 - $00:9FFF||$44||$08:8000 - $08:9FFF||$84||$10:8000 - $10:9FFF |- |$05||$00:A000 - $00:BFFF||$45||$08:A000 - $08:BFFF||$85||$10:A000 - $10:BFFF |- |$06||$00:C000 - $00:DFFF||$46||$08:C000 - $08:DFFF||$86||$10:C000 - $10:DFFF |- |$07||$00:E000 - $00:FFFF||$47||$08:E000 - $08:FFFF||$87||$10:E000 - $10:FFFF |- |$08||$01:0000 - $01:1FFF||$48||$09:0000 - $09:1FFF||$88||$11:0000 - $11:1FFF |- |$09||$01:2000 - $01:3FFF||$49||$09:2000 - $09:3FFF||$89||$11:2000 - $11:3FFF |- |$0A||$01:4000 - $01:5FFF||$4A||$09:4000 - $09:5FFF||$8A||$11:4000 - $11:5FFF |- |$0B||$01:6000 - $01:7FFF||$4B||$09:6000 - $09:7FFF||$8B||$11:6000 - $11:7FFF |- |$0C||$01:8000 - $01:9FFF||$4C||$09:8000 - $09:9FFF||$8C||$11:8000 - $11:9FFF |- |$0D||$01:A000 - $01:BFFF||$4D||$09:A000 - $09:BFFF||$8D||$11:A000 - $11:BFFF |- |$0E||$01:C000 - $01:DFFF||$4E||$09:C000 - $09:DFFF||$8E||$11:C000 - $11:DFFF |- |$0F||$01:E000 - $01:FFFF||$4F||$09:E000 - $09:FFFF||$8F||$11:E000 - $11:FFFF |- |$10||$02:0000 - $02:1FFF||$50||$0A:0000 - $0A:1FFF||$90||$12:0000 - $12:1FFF |- |$11||$02:2000 - $02:3FFF||$51||$0A:2000 - $0A:3FFF||$91||$12:2000 - $12:3FFF |- |$12||$02:4000 - $02:5FFF||$52||$0A:4000 - $0A:5FFF||$92||$12:4000 - $12:5FFF |- |$13||$02:6000 - $02:7FFF||$53||$0A:6000 - $0A:7FFF||$93||$12:6000 - $12:7FFF |- |$14||$02:8000 - $02:9FFF||$54||$0A:8000 - $0A:9FFF||$94||$12:8000 - $12:9FFF |- |$15||$02:A000 - $02:BFFF||$55||$0A:A000 - $0A:BFFF||$95||$12:A000 - $12:BFFF |- |$16||$02:C000 - $02:DFFF||$56||$0A:C000 - $0A:DFFF||$96||$12:C000 - $12:DFFF |- |$17||$02:E000 - $02:FFFF||$57||$0A:E000 - $0A:FFFF||$97||$12:E000 - $12:FFFF |- |$18||$03:0000 - $03:1FFF||$58||$0B:0000 - $0B:1FFF||$98||$13:0000 - $13:1FFF |- |$19||$03:2000 - $03:3FFF||$59||$0B:2000 - $0B:3FFF||$99||$13:2000 - $13:3FFF |- |$1A||$03:4000 - $03:5FFF||$5A||$0B:4000 - $0B:5FFF||$9A||$13:4000 - $13:5FFF |- |$1B||$03:6000 - $03:7FFF||$5B||$0B:6000 - $0B:7FFF||$9B||$13:6000 - $13:7FFF |- |$1C||$03:8000 - $03:9FFF||$5C||$0B:8000 - $0B:9FFF||$9C||$13:8000 - $13:9FFF |- |$1D||$03:A000 - $03:BFFF||$5D||$0B:A000 - $0B:BFFF||$9D||$13:A000 - $13:BFFF |- |$1E||$03:C000 - $03:DFFF||$5E||$0B:C000 - $0B:DFFF||$9E||$13:C000 - $13:DFFF |- |$1F||$03:E000 - $03:FFFF||$5F||$0B:E000 - $0B:FFFF||$9F||$13:E000 - $13:FFFF |- |$20||$04:0000 - $04:1FFF||$60||$0C:0000 - $0C:1FFF |- |$21||$04:2000 - $04:3FFF||$61||$0C:2000 - $0C:3FFF |- |$22||$04:4000 - $04:5FFF||$62||$0C:4000 - $0C:5FFF |- |$23||$04:6000 - $04:7FFF||$63||$0C:6000 - $0C:7FFF |- |$24||$04:8000 - $04:9FFF||$64||$0C:8000 - $0C:9FFF |- |$25||$04:A000 - $04:BFFF||$65||$0C:A000 - $0C:BFFF |- |$26||$04:C000 - $04:DFFF||$66||$0C:C000 - $0C:DFFF |- |$27||$04:E000 - $04:FFFF||$67||$0C:E000 - $0C:FFFF |- |$28||$05:0000 - $05:1FFF||$68||$0D:0000 - $0D:1FFF |- |$29||$05:2000 - $05:3FFF||$69||$0D:2000 - $0D:3FFF |- |$2A||$05:4000 - $05:5FFF||$6A||$0D:4000 - $0D:5FFF |- |$2B||$05:6000 - $05:7FFF||$6B||$0D:6000 - $0D:7FFF |- |$2C||$05:8000 - $05:9FFF||$6C||$0D:8000 - $0D:9FFF |- |$2D||$05:A000 - $05:BFFF||$6D||$0D:A000 - $0D:BFFF |- |$2E||$05:C000 - $05:DFFF||$6E||$0D:C000 - $0D:DFFF |- |$2F||$05:E000 - $05:FFFF||$6F||$0D:E000 - $0D:FFFF |- |$30||$06:0000 - $06:1FFF||$70||$0E:0000 - $0E:1FFF |- |$31||$06:2000 - $06:3FFF||$71||$0E:2000 - $0E:3FFF |- |$32||$06:4000 - $06:5FFF||$72||$0E:4000 - $0E:5FFF |- |$33||$06:6000 - $06:7FFF||$73||$0E:6000 - $0E:7FFF |- |$34||$06:8000 - $06:9FFF||$74||$0E:8000 - $0E:9FFF |- |$35||$06:A000 - $06:BFFF||$75||$0E:A000 - $0E:BFFF |- |$36||$06:C000 - $06:DFFF||$76||$0E:C000 - $0E:DFFF |- |$37||$06:E000 - $06:FFFF||$77||$0E:E000 - $0E:FFFF |- |$38||$07:0000 - $07:1FFF||$78||$0F:0000 - $0F:1FFF |- |$39||$07:2000 - $07:3FFF||$79||$0F:2000 - $0F:3FFF |- |$3A||$07:4000 - $07:5FFF||$7A||$0F:4000 - $0F:5FFF |- |$3B||$07:6000 - $07:7FFF||$7B||$0F:6000 - $0F:7FFF |- |$3C||$07:8000 - $07:9FFF||$7C||$0F:8000 - $0F:9FFF |- |$3D||$07:A000 - $07:BFFF||$7D||$0F:A000 - $0F:BFFF |- |$3E||$07:C000 - $07:DFFF||$7E||$0F:C000 - $0F:DFFF |- |$3F||$07:E000 - $07:FFFF||$7F||$0F:E000 - $0F:FFFF |}
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F256 Foenix:Copyrights
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