Name            Simple Serial Card;
Partno          SSC0001;
Revision        01;
Date            3/9/23;
Designer        Chris RYU;
Company         RyuCats;
Location        None;
Assembly        None;
Device          g22v10;

/* Inputs */

Pin 1 = reset;
Pin 2 = CTS;
Pin 3 = io_C800;
Pin 4 = slot_select;
Pin 5 = io_slot_access;
Pin 6 = RW;
Pin 7 = A11;
Pin 8 = A10;
Pin 9 = A9;
Pin 10 = A8;
Pin 11 = A3;

/* Outputs */

Pin 14 = rom_c800_enable;
Pin 15 = rom_latch;
Pin 16 = ls245_enable;
Pin 17 = eprom_a8;
Pin 18 = eprom_a9;
Pin 19 = eprom_a10;
Pin 20 = rom_enable;
Pin 21 = PHI2;
Pin 22 = d0;

/*  Latch (RS flip-flop) definition:
    Q  = (Q & RESET) # !SET;
*/

PHI2 = !slot_select; /* per schematic */

cf00_access = io_C800 # !A8 # !A9 # !A10; /* CF00 access, pull low */

/* 
    if either reset or cf00 access is pulled low, then rom_latch = 1
    if io_slot_access is 0, then rom_latch = 0
    if io_slot_access is 1, then rom_latch = no change
*/
rom_latch = (rom_latch & io_slot_access) # !(reset & cf00_access);
rom_c800_enable = rom_latch # io_C800; /* enable if both pulled low */

ls245_enable = ( io_slot_access & rom_c800_enable & slot_select); /* c800 ? */
rom_enable = (io_slot_access & rom_c800_enable);

eprom_a8 = A8 # !A11;
eprom_a9 = A9 # !A11;
eprom_a10 = A10 # !A11;