46 lines
1.9 KiB
Plaintext
Executable File
46 lines
1.9 KiB
Plaintext
Executable File
Name PC I/O decoder PAL;
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Partno PC 1;
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Date 25/02/88;
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Revision 01;
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Designer P.D. Smart;
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Company Feduptronics;
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Assembly XXXXX;
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Location XXXXX;
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/******************************************************************/
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/* A PAL to decode the IBM PC I/O space to generate 4 select */
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/* signals for I/O devices in the range 0210-0211 hex. Also */
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/* generates a 74LS245 select signal. */
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/******************************************************************/
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/* Allowable Target Device Types: 16L8 */
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/******************************************************************/
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/** Inputs **/
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Pin [1..2] = [A0..1] ; /* PC bus address signals */
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Pin [3..9] = [A3..9] ; /* */
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Pin 11 = CPUAEN ; /* CPUAEN signal from PC bus */
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Pin 13 = IOWR ; /* I/O write strobe */
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Pin 14 = IORD ; /* I/O read strobe */
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/** Outputs **/
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Pin 15 = ADDR ; /* Intermediate address output */
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Pin 16 = WRPCL ; /* Write LINK signal */
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Pin 17 = RDPCL ; /* Read LINK signal */
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Pin 18 = WRCOM ; /* Write command */
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Pin 19 = RDSTAT ; /* Read status */
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Pin 12 = SEL245 ; /* Select 245 */
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/** Declarations and Intermediate Variable Definitions **/
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/** Logic Equations **/
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ADDR = A3 # !A4 # A5 # A6 # A7 # A8 # !A9;
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WRPCL = !(CPUAEN # IOWR # !IORD # ADDR # A0 # A1);
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RDPCL = CPUAEN # !IOWR # IORD # ADDR # A0 # A1;
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WRCOM = !(CPUAEN # IOWR # !IORD # ADDR # !A0 # A1);
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RDSTAT = CPUAEN # !IOWR # IORD # ADDR # !A0 # A1;
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SEL245 = CPUAEN # (IOWR & IORD) # ADDR;
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