mirror of https://github.com/RevCurtisP/C02.git
153 lines
5.9 KiB
Plaintext
153 lines
5.9 KiB
Plaintext
;Extended Memory Assembly Language Routines Non-Functional Template
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;Requires locations XMBANK and XMADDR (header.a02)
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SUBROUTINE XMEMORY
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;Extended Memory Constants\
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XLBANK EQU $00 ;Maximum Logical Bank - 0 = Not Implemented
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;Extended Memory Physical Address Registers - Defined in header.a02
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;XMBANK Bank These contain the physical bank and address of extended memory,
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;XMADDR Address which are usually different than the logical bank and address.
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;Bank Selected Memory
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;This interface is used by nearly every 6502 based 8-bit computer
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;The extended memory is exposed as a 1K, 8K, or 16K section of the
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;6502's address space. An I/O register is used to to map equally
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;sized banks of the extended memory into this section of RAM.
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;XMBANK is the bank number and XMADDR is the offset in the bank.
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;Bank Physical Address Max Ext
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;Size XMBANK XMADDR Logical Address RAM
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; 1K BBBBBBBB 000000AA AAAAAAAA 000000BB BBBBBBAA AAAAAAAA 256K
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; 8K BBBBBBBB 00000AAA AAAAAAAA 00000BBB BBBBBAAA AAAAAAAA 512K
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; 16K BBBBBBBB 0000AAAA AAAAAAAA 0000BBBB BBBBAAAA AAAAAAAA 1024K
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;Ultimem for the VIC-20 uses a two-byte bank number and 8K banks
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;giving a 27-bit wide address, but this module is limited to 24 bits.
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; Physical Address Max Ext
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; XMBANK XMADDR Logical Address RAM
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;000BBBBB BBBBBBBB 00000AAA AAAAAAAA BBBBBBBB BBBBBAAA AAAAAAAA 16MB
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;Page Selected Memory
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;The interface is used by GeoRAM for the Commodore 64 and 128
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;The extended memory is exposed as a single page (256 bytes) of the
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;6502's address space. I/O registers are used to select a bank of
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;up to 64K of extended memory and to map a page of that bank to
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;the page of RAM. GeoRAM uses 16K banks.
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;XMBANK is the bank number, the high byte of XMADDR is the page of
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;the bank, and the low byte of XMADDR is the offset in the page.
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;Bank XMBANK XMADDR Max Ext
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;Size Bank Page Offset Logical Address RAM
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; 16K BBBBBBBB 0000PPPP AAAAAAAA 0000BBBB BBBBPPPP AAAAAAAA 1MB
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; 64K BBBBBBBB PPPPPPPP AAAAAAAA BBBBBBBB PPPPPPPP AAAAAAAA 16MB
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;DMA Controller`
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;This interface is used by the Commodore REUs and the run6502 emulator.
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;The expansion device suspends operation of the 6502 and directly
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;reads and writes to the system RAM. I/O registers are used to select
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;an operation (read, write, or swap), a 24-bit extended memory address,
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;a 16-bit system RAM address, and 16-bit byte count.
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;XMBANK and XMADDR contain the 24-bit extended memory address which is
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;identical to the logical address, for up to 16MB of extended memory.
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;xgetad() - Get Logical Extended Memory Address
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; For run6502, this is the same as the Physical Address
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;Returns: A = Logical Bank ($00-$0F)
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; YX = Logical Address ($0000-$FFFF)
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XGETAD: LDA #$FF ;Return $FF,$FFFFF which would
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TAY ;indicate 16MB of extended memory,
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TAX ;which is rare on 8-bit machines
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RTS
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;xsetad() - Set Logical Extended Memory Address
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; For run6502, this is the same as the Physical Address
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;Args: A = Logical Bank ($00-$0F)
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; YX = Logical Address ($0000-$FFFF)
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;Returns: A=$00 - Success or $FF - Failure
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XSETAD: LDA #$FF ;Return Failure
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;xputc() - Write Byte to Extended Memory
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;Args: A = Byte
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;Affects: A,X
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XPUTC: RTS
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;xgetc() - Read Byte from Extended Memory
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;Returns: A = Byte
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XGETC: LDA #0 ;Return 0
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RTS
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;xputi() - Write Word to Extended Memory
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;Args: YX = Word
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XPUTI: RTS
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;xgeti() - Read Word from Extended Memory
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;Returns: YX = Word
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XGETI: LDY #0 ;Return Zero
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LDX #0
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RTS
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;xgetl() - Read Long from Extended Memory
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;Args: AYX = Long
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XGETL: LDA #0 ;Return Zero
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;xputl() - Write Long to Extended Memory
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;Args: AYX = Long
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XPUTL: RTS
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;xread(n,dest) - Read Bytes from Extended Memory
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;Args: A = Number of Bytes to Read (0=256)
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; YX = Destination Address
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;Returns: AYX = New Extended Memory Address
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XREAD: ;Return $FF,$FFF
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;xwrite(n,source) - Write Bytes to Extended Memory
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;Args: A = Number of Bytes to Write (0=256)
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; YX = Source Address
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;Returns: AYX = New Extended Memory Address
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XWRITE: ;Return $FF,$FFF
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;xswap(n,dest) - Swap Bytes with Extended Memory
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;Args: A = Number of Bytes to Exchange
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; YX = System Memory Address
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;Returns: AYX = New Extended Memory Address
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XSWAP: ;Return $FF,$FFF
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;xload(addr) - Load from Extended Memory
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;Args: YX = Local Memory End Address
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;Uses: GETDST - Local Memory Start Address
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;Returns: AYX = New Extended Memory Address
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XLOAD: ;Return $FF,$FFF
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;xsave(size) - Save from Extended Memory
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;Args: YX = Local Memory End Address
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;Requires: SRCPTR = Local Memory Start Address
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;Returns: AYX = New Extended Memory Address
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XSAVE: ;Return $FF,$FFF
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;xchng(size) - Exchange with Extended Memory
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;Args: YX = Local Memory End Address
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;Requires: DSTPTR = Local Memory Start Address
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;Returns: AYX = New Extended Memory Address
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XCHNG: ;Return $FF,$FFF
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;xrpage(count, page) - Read Extended Memory Pages
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;Args: A = Number of Pages
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; Y = Local Memory Starting Page
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;Returns: AYX = New Extended Memory Address
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XRPAGE: ;Return $FF,$FFF
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;xwpage(count, page) - Write Extended Memory Pages
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;Args: A = Number of Pages
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; Y = Local Memory Starting Page
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;Returns: AYX = New Extended Memory Address
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XWPAGE: ;Return $FF,$FFF
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;xspage(count, page) - Swap Extended Memory Pages
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;Args: A = Number of Pages
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; Y = Local Memory Starting Page
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;Returns: AYX = New Extended Memory Address
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XSPAGE: LDA #$FF ;Return $FF,$FFF
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TAY
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TAX
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RTS
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ENDSUBROUTINE |