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121 lines
5.3 KiB
Plaintext
121 lines
5.3 KiB
Plaintext
Template Functions for C02 Programs
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This module provides functions to read from and write to extended
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memory.
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Extended memory is RAM that is not directly addressable by the 6502.
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Read and write operations use a 24-bit logical address, which is
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comprised of an 8-bit bank and 16-bit offset and automatically updated
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after each operation.
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At the beginning of the program use the directives
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#include <stddef.h02>
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#include <xmemory.h02>
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The following functions are defined:
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b,d = xgetad(); Returns the current logical extended bank b
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and offset d.
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Note: the physical address stored in XMBANK
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and XMADDR is converted to a logical bank and
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offset, which are returned.
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xsetad(b,d); Sets the current logical extended bank to b
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and offset to d.
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This extended address is used for all read and
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write functions except for the page operations.
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Note: the logical address is converted to a
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physical address stored in XMBANK and XMADDR.
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c = xgetc(); Reads a byte from the current extended address,
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increments the address, and returns the byte
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as c.
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xputc(c); Writes byte c to the current extended address,
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then increments the address.
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w = xgeti(); Reads a word starting at the current extended
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address, adds 2 to the address, and returns the
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word as w.
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xputi(w); Writes word w at the current extended address,
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then adds 2 to the address.
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c,w = xgetl(); Reads a long starting at the current extended
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address, adds 3 to the address, and returns the
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high byte of the long in c and the low word in w.
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xputl(c,w); Writes the long consisting of the byte c and
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word w at the current extended address, then
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adds 3 to the address.
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xread(n,r); Reads n bytes starting at the current extended
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address into array r, then adds n to the address.
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xwrite(n,r); Writes n bytes of array r starting at the current
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extended address, then adds n to the address.
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xswap(n,r); Swaps n bytes of array r with n bytes starting at
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the current extended address, then adds n to the
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address.
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xload(w); Reads word w bytes into local memory starting at
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the address specified by a call to setdst() from
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extended memory starting at the current extended
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address, then adds w to the address.
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xsave(w); Writes word w bytes from local memory starting at
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the address specified by a call to setsrc() into
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extended memory starting at the current extended
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address, then adds w to the address.
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xchng(w); Swaps word w bytes in local memory starting at
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the address specified by a call to setdst() with
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extended memory starting at the current extended
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address, then adds w to the address.
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xsetpg(b,p) Sets the current extended address to bank b and
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offset p * 256. This ensures that the address is
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on a page boundary for subsequent page read and
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write operations.
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Note: The page operation are the fastest of the
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block read and write functions since the code
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can use indirect addressing.
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xrpage(n,p); Copies n 256 byte pages starting at the current
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extended bank and page to local memory starting
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at address p * 256, then updates the extended
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address accordingly.
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xwpage(n,p); Copies n 256 bytes from local memory starting
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at address p * 256 to extended memory starting at
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current bank and page, then updates the extended
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address accordingly.
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xspage(n,p); Swaps n 256 bytes from local memory starting at
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address p * 256 with extended memory starting at
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current bank and page, then updates the extended
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address accordingly.
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Note: This library expects the following functions to be defined:
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getdst(); Get Destination Pointer
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getsrc(); Get Source Pointer
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resrxy(); Restore X and Y Registers
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savrxy(); Save X and Y Registers
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along with the zero page variables
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dstptr,srcptr: Destination and Source Pointer
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and the external variables
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xmaddr,xmbank; Extended Memory Address and Bank
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temp1,temp2: Temporary storage
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