Raimon @ quifisraimon
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- [NEW] Afegida la rom de Combat. - [NEW] Afegit mòdul "rom" - [NEW] Ampliats stubs de "mem", "tia" i "pia"
240 lines
10 KiB
Plaintext
240 lines
10 KiB
Plaintext
From: https://forums.atariage.com/topic/192418-mirrored-memory/
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THE 6507 PROCESSOR
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===============================================================================
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The 6507 chip has only 13 address pins (A0 through A12) so the usable addresses
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are an 8K block from $0000 through $1FFF. Internally the 6507 still uses 16-bit
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addresses, but since there are no pins for A13 through A15, any attempt to
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access $2000 through $FFFF will actually access $0000 through $1FFF:
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$E000 - $FFFF = 8K mirror of $0000 - $1FFF
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$C000 - $DFFF = 8K mirror of $0000 - $1FFF
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$A000 - $BFFF = 8K mirror of $0000 - $1FFF
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$8000 - $9FFF = 8K mirror of $0000 - $1FFF
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$6000 - $7FFF = 8K mirror of $0000 - $1FFF
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$4000 - $5FFF = 8K mirror of $0000 - $1FFF
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$2000 - $3FFF = 8K mirror of $0000 - $1FFF
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$0000 - $1FFF = 8K of addressable memory
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The cartridge slot, 6532 RIOT chip, and TIA chip have addresses within the 8K
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memory block at $0000 - $1FFF, so they have mirrors in the other 8K memory
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blocks. For simplicity, only mirrors within $0000 - $1FFF will be listed below,
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with the others being understood.
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THE CARTRIDGE SLOT
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===============================================================================
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The 2600's 4K cartridge slot has 12 address lines (A0-A11). A12 acts as a chip
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select and is wired as 1, so the addresses are %xxx1 ???? ???? ????, where "x"
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is "don't care" and "?" can be 0 or 1, giving addresses of $1000 - $1FFF.
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If a cartridge has only 2K, then A11 isn't connected, in which case the
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addresses are %xxx1 x??? ???? ????:
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$1800 - $1FFF = 2K mirror of $1000 - $17FF
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$1000 - $17FF = 2K of addressable ROM
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If a cartridge includes the 128-byte SARA chip for extra RAM, the SARA chip
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uses A7 for the R/W line:
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$1100 - $1FFF = 3.75K of addressable ROM
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$1080 - $10FF = 128 bytes of SARA RAM read addresses
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$1000 - $107F = 128 bytes of SARA RAM write addresses
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There are other cartridge formats that add extra RAM, but I won't try to list
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their mappings.
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THE 6532 RIOT CHIP
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===============================================================================
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The 6532 RIOT chip has only seven (7) address pins (A0-A6). The chip selects
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are connected to A12 (which must be 0) and A7 (which must be 1). There is also
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a RAM select, which is connected to A9.
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To read or write the RIOT RAM, the RAM select (A9) must be 0, giving addresses
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of %xxx0 xx0x 1??? ????:
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$0D80 - $0DFF = mirror of the RIOT RAM
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$0C80 - $0CFF = mirror of the RIOT RAM
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$0980 - $09FF = mirror of the RIOT RAM
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$0880 - $08FF = mirror of the RIOT RAM
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$0580 - $05FF = mirror of the RIOT RAM
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$0480 - $04FF = mirror of the RIOT RAM
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$0180 - $01FF = mirror of the RIOT RAM (used by the 6507 for its stack memory)
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$0080 - $00FF = 128 bytes of RIOT RAM
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To access the RIOT's I/O or timer functions, the RAM select (A9) must be 1,
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theoretically giving addresses of %xxx0 xx1x 1??? ????. However, the RIOT's I/O
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and timer functions don't use all seven address pins.
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To access the I/O functions, A2 must be 0, and only A0 and A1 (and A2) are used
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for addresses, so the I/O addresses are %xxx0 xx1x 1xxx x0??:
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$0Fxx, $0Exx, $0Bxx, $0Axx, $07xx, $06xx, $03xx = same mirrors as $02xx shown below
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$02F8 - $02FB = mirror of $0280 - $0283
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$02F0 - $02F3 = mirror of $0280 - $0283
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$02E8 - $02EB = mirror of $0280 - $0283
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$02E0 - $02E3 = mirror of $0280 - $0283
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$02D8 - $02DB = mirror of $0280 - $0283
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$02D0 - $02D3 = mirror of $0280 - $0283
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$02C8 - $02CB = mirror of $0280 - $0283
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$02C0 - $02C3 = mirror of $0280 - $0283
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$02B8 - $02BB = mirror of $0280 - $0283
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$02B0 - $02B3 = mirror of $0280 - $0283
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$02A8 - $02AB = mirror of $0280 - $0283
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$02A0 - $02A3 = mirror of $0280 - $0283
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$0298 - $029B = mirror of $0280 - $0283
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$0290 - $0293 = mirror of $0280 - $0283
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$0288 - $028B = mirror of $0280 - $0283
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$0283 = data-direction control for I/O register B
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$0282 = I/O register B
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$0281 = data-direction control for I/O register A
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$0280 = I/O register A
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To access the timer functions, A2 must be 1, and only A0, A1, A3, and A4 (and A2)
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are used for addresses-- although A1, A3, and A4 aren't always used.
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To set (write) the timer, A4 must be 1, A3 enables or disables the timer
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interrupt, and A0 and A1 select the timer interval, so the addresses are
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%xxx0 xx1x 1xx1 ?1??:
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$0Fxx, $0Exx, $0Bxx, $0Axx, $07xx, $06xx, $03xx = same mirrors as $02xx shown below
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$02FC - $02FF = mirror of $029C - $029F
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$02F4 - $02F7 = mirror of $0294 - $0297
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$02DC - $02DF = mirror of $029C - $029F
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$02D4 - $02D7 = mirror of $0294 - $0297
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$02BC - $02BF = mirror of $029C - $029F
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$02B4 - $02B7 = mirror of $0294 - $0297
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$029F = enable the timer interrupt and set the timer using the 1024-cycle interval
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$029E = enable the timer interrupt and set the timer using the 64-cycle interval
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$029D = enable the timer interrupt and set the timer using the 8-cycle interval
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$029C = enable the timer interrupt and set the timer using the 1-cycle interval
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$0297 = disable the timer interrupt and set the timer using the 1024-cycle interval
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$0296 = disable the timer interrupt and set the timer using the 64-cycle interval
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$0295 = disable the timer interrupt and set the timer using the 8-cycle interval
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$0294 = disable the timer interrupt and set the timer using the 1-cycle interval
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To read the timer, A0 must be 0, A3 enables or disables the timer interrupt,
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and A1 and A4 aren't used, so the addresses are %xxx0 xx1x 1xxx ?1x0:
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$0Fxx, $0Exx, $0Bxx, $0Axx, $07xx, $06xx, $03xx = same mirrors as $02xx shown below
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$02Ax - $02Fx = same mirrors as $029x shown below
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$029E, $029C, $0296, $0294 = mirrors of $028E, $028C, $0286, and $0284
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$028E = mirror of $028C
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$028C = enable the timer interrupt and read the timer
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$0286 = mirror of $0284
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$0284 = disable the timer interrupt and read the timer
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To read the timer interrupt flag and PA7 interrupt flag, A0 must be 1, and A1,
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A3, and A4 aren't used, so the addresses are %xxx0 xx1x 1xxx x1x1:
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$0Fxx, $0Exx, $0Bxx, $0Axx, $07xx, $06xx, $03xx = same mirrors as $02xx shown below
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$029x - $02Fx = same mirrors as $028x shown below
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$028F, $028D, $0287 = mirrors of $0285
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$0285 = read the interrupt flags
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To set (write) the PA7 edge-detect control, A4 must be 0, A0 selects positive
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or negative edge-detect, A1 enables or disables the PA7 interrupt, and A3 isn't
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used, so the addresses are %xxx0 xx1x 1xx0 x1??:
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$0Fxx, $0Exx, $0Bxx, $0Axx, $07xx, $06xx, $03xx = same mirrors as $02xx shown below
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$02Ax, $02Cx, $02Ex = same mirrors as $028x shown below
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$028C - $028F = mirrors of $0284 - $0287
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$0287 = enable the PA7 interrupt and select positive edge-detect
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$0286 = enable the PA7 interrupt and select negative edge-detect
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$0285 = disable the PA7 interrupt and select positive edge-detect
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$0284 = disable the PA7 interrupt and select negative edge-detect
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As seen above, the RIOT's mirrors are rather complex. Where any mirrors seem to
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conflict with other mirrors, the R/W and RAM select lines determine which
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mirrors will be in effect.
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THE TIA CHIP
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===============================================================================
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The TIA chip has only six (6) address pins-- A0 through A5. The chip selects
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are connected to A12 (which must be 0) and A7 (which must be 0).
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The TIA's write registers use all six address pins, so the addresses are
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%xxx0 xxxx 0x?? ????:
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$01xx - $0Fxx = same mirrors as $00xx shown below
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$0040 - $007F = mirror of $0000 - $003F
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$002D - $003F = not used
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$002C = CXCLR (clear collision latches)
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$002B = HMCLR (clear horizontal motion registers)
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$002A = HMOVE (apply horizontal motion)
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$0029 = RESMP1 (reset missile 1 to player 1)
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$0028 = RESMP0 (reset missile 0 to player 0)
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$0027 = VDELBL (vertical delay ball)
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$0026 = VDELP1 (vertical delay player 1)
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$0025 = VDELP0 (vertical delay player 0)
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$0024 = HMBL (horizontal motion ball)
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$0023 = HMM1 (horizontal motion missile 1)
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$0022 = HMM0 (horizontal motion missile 0)
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$0021 = HMP1 (horizontal motion player 1)
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$0020 = HMP0 (horizontal motion player 0)
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$001F = ENABL (enable ball graphics)
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$001E = ENAM1 (enable missile 1 graphics)
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$001D = ENAM0 (enable missile 0 graphics)
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$001C = GRP1 (graphics player 1)
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$001B = GRP0 (graphics player 0)
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$001A = AUDV1 (audio volume 1)
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$0019 = AUDV0 (audio volume 0)
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$0018 = AUDF1 (audio frequency 1)
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$0017 = AUDF0 (audio frequency 0)
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$0016 = AUDC1 (audio control 1)
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$0015 = AUDC0 (audio control 0)
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$0014 = RESBL (reset ball)
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$0013 = RESM1 (reset missile 1)
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$0012 = RESM0 (reset missile 0)
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$0011 = RESP1 (reset player 1)
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$0010 = RESP0 (reset player 0)
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$000F = PF2 (playfield register byte 2)
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$000E = PF1 (playfield register byte 1)
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$000D = PF0 (playfield register byte 0)
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$000C = REFP1 (reflect player 1)
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$000B = REFP0 (reflect player 0)
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$000A = CTRLPF (control playfield ball size and reflect)
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$0009 = COLUBK (color-lum background)
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$0008 = COLUPF (color-lum playfield)
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$0007 = COLUP1 (color-lum player 1)
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$0006 = COLUP0 (color-lum player 0)
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$0005 = NUSIZ1 (number-size player-missile 1)
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$0004 = NUSIZ0 (number-size player-missile 0)
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$0003 = RSYNC (reset horizontal sync counter)
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$0002 = WSYNC (wait for leading edge of horizontal blank)
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$0001 = VBLANK (vertical blank set-clear)
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$0000 = VSYNC (vertical sync set-clear)
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The TIA's read registers do not use A4 and A5, so the addresses are
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%xxx0 xxxx 0xxx ????:
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$01xx - $0Fxx = same mirrors as $00xx shown below
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$001x - $007x = mirrors of $0000 - $000F
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$000E - $000F = not used
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$000D = INPT5 (input port 5, trigger 1)
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$000C = INPT4 (input port 4, trigger 0)
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$000B = INPT3 (input port 3, pot 3)
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$000A = INPT2 (input port 2, pot 2)
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$0009 = INPT1 (input port 1, pot 1)
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$0008 = INPT0 (input port 0, pot 0)
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$0007 = CXPPMM (collision of players and missiles)
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$0006 = CXBLPF (collision of ball with playfield)
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$0005 = CXM1FB (collision of missile 1 with playfield-ball)
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$0004 = CXM0FB (collision of missile 0 with playfield-ball)
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$0003 = CXP1FB (collision of player 1 with playfield-ball)
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$0002 = CXP0FB (collision of player 0 with playfield-ball)
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$0001 = CXM1P (collision of missile 1 with players)
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$0000 = CXM0P (collision of missile 0 with players)
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As with the RIOT mirrors, some TIA mirrors seem to conflict, but the R/W line
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determines which mirrors will be in effect.
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