PAL source code for the Sega Mega Drive development kit

gistfile1.txt

Title   Sega Megadrive dev system PAL #1
; special 26v12 version
revision 2
date    1994-04-01
company Synchron Data
author  Tore
Pattern 0A
;Buggfixes:
;Eprom_cs buggfixed
;changed sega d7 strobe to d15 and same adress as datareadlatch


chip gal1 palce26v12

;INPUT
PIN 1   write_disable         ;0=write disabled, 1=normal RW operation
PIN 2   map
PIN 3   HOST_RESET              ;aktiv l†g
PIN 4   sega_lo_we
PIN 5   sega_hi_we
PIN 6   sega_cs

PIN 8   sega_oe
PIN 9   reset
PIN 10  A18
PIN 11  A19
PIN 12  A20
PIN 13  A21
PIN 14  toggle_strobe           ;toggle bit from ls74
PIN 28  toggle_read_oe

;OUTPUT
PIN 15  EPROM_CS
PIN 16  READ_LATCH1_OE
PIN 17  READ_LATCH2_OE
PIN 18  RESET_BUTTON
PIN 19  WRT_LATCH1_LE
PIN 20  WRT_LATCH2_LE


PIN 22  WRT_LATCH3_LE
PIN 23  sega_d15
PIN 24  Sram_cs
pin 25  sram_lo_we
pin 26  sram_hi_we
pin 27  Write_warning

;----------------------------------------------------------
equations

;Main chipselect f”r srambanken
/Sram_cs        = /a21 * /sega_cs * map;

;Write strobe till Srambanken
/sram_lo_we  = /a21 * write_disable * /sega_lo_we;
/sram_hi_we  = /a21 * write_disable * /sega_hi_we;

;Write warning pulse som kopplas till en extern ls74 eller dyl
Write_warning= /sega_lo_we * /write_disable * /a21 * /sega_cs
             + /sega_hi_we * /write_disable * /a21 * /sega_cs;

;Eprom select signalen
/EPROM_CS =
        /sega_cs * /sega_oe * /a18 * /a19 * /a20 *  a21 *  map + ;normalt
        /sega_cs * /sega_oe * /map * /a21                        ;boot

/READ_LATCH1_OE = a18 * /a19 * /a20 * a21 * /sega_cs * /sega_oe * map;

sega_d15.TRST   = a18 * /a19 * /a20 * a21 * /sega_cs * /sega_oe * map;

/READ_LATCH2_OE =/a18 *  a19 * /a20 * a21 * /sega_cs * /sega_oe * map;
 WRT_LATCH1_LE  =/a18 * /a19 *  a20 * a21 * /sega_cs * sega_oe * map;
 WRT_LATCH2_LE  = a18 * /a19 *  a20 * a21 * /sega_cs * sega_oe * map;
 WRT_LATCH3_LE  =/a18 *  a19 *  a20 * a21 * /sega_cs * sega_oe * map;

sega_d15        = toggle_strobe;

RESET_BUTTON    = /HOST_RESET