MyCpu/GAL/Decoder/DECODER.PLD at main · fortinsylvain/MyCpu · GitHub

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Name     DECODER;
PartNo   1;
Revision 1.0;
Date     8/12/25;
Designer Sylvain Fortin;
Company  YourCompany;
Assembly Home;
Location Montreal;
Device   g22v10;

/*
                               ______________
                              |   DECODER    |
                    I/CLK x---|1           24|---x Vcc
                A10     I x---|2           23|---x I/O/Q DEC0_CS_N
                A11     I x---|3           22|---x I/O/Q DEC1_CS_N
                A12     I x---|4           21|---x I/O/Q
                A13     I x---|5           20|---x I/O/Q
                A14     I x---|6           19|---x I/O/Q RAM_CS_N
                A15     I x---|7           18|---x I/O/Q
                E_N     I x---|8           17|---x I/O/Q
                A0      I x---|9           16|---x I/O/Q
                A1      I x---|10          15|---x I/O/Q LED_PORT_CLK
                RW      I x---|11          14|---x I/O/Q EEPROM_CS_N
                      GND x---|12          13|---x I
                              |______________|

*/

/** Input Pins **/
Pin 2  = A10;
Pin 3  = A11;
Pin 4  = A12;
Pin 5  = A13;
Pin 6  = A14;
Pin 7  = A15;
Pin 8  = E_N;
Pin 9  = A0;
Pin 10 = A1;
Pin 11 = RW;

/** Output Pins **/
Pin 14 = EEPROM_CS_N;
Pin 15 = LED_PORT_CLK;
Pin 19 = RAM_CS_N;
Pin 22 = DEC1_CS_N;
Pin 23 = DEC0_CS_N;

/*
0x0000 - 0x1FFF   RAM
0x7C00 - 0x7FFF   LCD
0xC000 - 0xDFFF   LED_PORT
0xE000 - 0xFFFF   EEPROM
*/

/** !RAM_CS_N     = (!E_N & !A15 & !A14 & !A13); **/
/** For a read immediate CS_N but for a write use E_N **/
!RAM_CS_N     = (RW & !A15 & !A14 & !A13) # (!RW & !E_N & !A15 & !A14 & !A13);

DEC0_CS_N = (!E_N & !A15 & A14 & A13 & A12 & A11 & A10);

!LED_PORT_CLK = (!E_N &  A15 &  A14 & !A13);

/** !EEPROM_CS_N  = (!E_N &  A15 &  A14 &  A13);  **/
!EEPROM_CS_N  = (A15 &  A14 &  A13);	/** Immediately activate the CS_N when address is in range to speed-up **/