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||      FILE:   #9005.PLD
||      PROJ:   20130517        
||      PART:   G20V8-#9005
||
||      DEV :   GAL20V8
||
||      DESC:   I/O DECODER & CONTROL
||
|
|GAL20V8A
|
|| INPUT
|  1:A1, 2:A2, 3:A3, 4:A4, 5:A5, 6:A6, 7:A7, 8:IO0, 9:RW, 10:PHI2,
|  11:EN, 13:RDYN, 14:RAMN, 23:-, 
|| OUTPUT 
|  22:DBE, 21:VDC, 20:PIA, 19:WFF, 18:CRD, 17:CWE, 16:RD, 15:WIO
|
| SIGNATURE: "9005    "
|
|  ACTIVE-LOW: DBE, VDC, PIA, WFF, CRD, CWE, RD, WIO
|
|  PROPERTY: "SIMPLE"
|
|| --------------------------------------------------------
|| IO SELECT => FF70-FF77 (65C02) - FC70-FC77 (65C816)
|  IOS  = (IO0' & A7' & A6 & A5 & A4 & A3')
|| R6545/HD6445 => FF70-FF71 / FC70-FC71
|  CRTC = (IOS & A2' & A1')
|| REGISTRO WRITE ONLY => FF72
|  WREG = (IOS & A2' & A1 & RW')
|| PIA 65C21 => FF74-FF77 / FC74-FC77
|  PIAS = (IOS & A2)
|| RD => segnale OE per RAM
|  RD = (RW & PHI2)
|| CRD, CWE => segnali read,write per HD6545 (qualificati con EN)
|  CRD = (CRTC & RW & EN)
|  CWE = (CRTC & RW' & EN)
|| ABILITAZIONE CRTC e PIA
|  PIA = PIAS
|  VDC = CRTC
|| CLOCK per registro FF
|  WFF = (WREG & RDYN)
|| SEGNALE WAIT I/O
|  WIO = (CRTC # WREG)
|| SEGNALE ABILITAZIONE 74x245
|  DBEIO = ((CRTC & EN) # (WREG & (EN # RDYN)) # (PIAS & PHI2))
|  DBEM  = RAMN'
|  DBE = (DBEIO # DBEM)