56 lines
2.0 KiB
Plaintext
56 lines
2.0 KiB
Plaintext
Name PicoPal;
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Partno U5;
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Date 27/11/22;
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Revision 01;
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Designer David Kuder;
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Company Grizzly Adams;
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Assembly None;
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Location None;
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Device g16V8;
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/****************************************************************/
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/* */
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/* Apple II Pi Pico Address Logic */
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/* */
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/****************************************************************/
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/* Allowable Target Device Types : PAL16V8 */
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/****************************************************************/
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/** Inputs **/
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PIN 1 = CLOCK; /* Unused Register Clock */
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PIN 2 = !RESET; /* System Reset */
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PIN [3..6] = [BSEL3..0]; /* Buffer Mode Select */
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PIN 7 = !DEVSELECT; /* $C0nX Selected -> 16B I/O */
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PIN 8 = !IOSELECT; /* $CnXX Selected -> Base ROM */
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PIN 9 = !IOSTROBE; /* $C8XX Selected -> Extd ROM */
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PIN 11 = A2;
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PIN 13 = A1;
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PIN 14 = A0;
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/** Outputs **/
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PIN 12 = !CARDSELECT; /* Card Select */
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/** Logic Overflow **/
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PIN 15 = EXTOFF; /* Combinatorial */
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PIN 16 = EXTSELECT; /* Combinatorial */
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PIN 17 = EXTENABLE; /* Combinatorial */
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PIN 18 = EXTDISABLE; /* Combinatorial */
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/** Logic Equations **/
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/* $CFxx disables, but only triggered during AddrLo */
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EXTOFF = IOSTROBE & [A2..0]:'b'111 & [BSEL3..0]:'b'101X;
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/* Implement an SR Latch */
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EXTDISABLE = !(EXTENABLE # IOSELECT);
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EXTENABLE = !(EXTDISABLE # RESET # EXTOFF # [BSEL3..0]:'b'0111);
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/* $C8XX and extended rom is enabled */
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EXTSELECT = EXTENABLE & IOSTROBE;
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/* Tell the Pico that the Apple wants attention. */
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CARDSELECT = DEVSELECT # IOSELECT # EXTSELECT;
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