LISTING FOR LOGIC DESCRIPTION FILE: u303.pld                         Page 1

CUPL: Universal Compiler for Programmable Logic
Version 4.0a Serial# MD-40A-8380
Copyright (C)  1983,1990 Logical Devices, Inc.
Created Fri Jan 04 02:50:57 1980

  1:        PARTNO          U303 ;
  2:        NAME            U303 ;
  3:        DATE            July 9, 1992 ;
  4:        REV             0 ;
  5:        DESIGNER        Dave Haynie ;
  6:        COMPANY         Commodore ;
  7:        ASSEMBLY        A3090 ;
  8:        LOCATION        West Chester ;
  9:        DEVICE          p22v10 ;
 10:
 11:/************************************************************************/
 12:/*                                                                      */
 13:/*      A3090   Zorro III/SCSI Arbiter                                  */
 14:/*                                                                      */
 15:/*      This device manages arbitration of the A3090 and Zorro III      */
 16:/*      buses.                                                          */
 17:/*                                                                      */
 18:/************************************************************************/
 19:/*                                                                      */
 20:/* DEVICE DATA:                                                         */
 21:/*                                                                      */
 22:/*      Device:         22V10-15                                        */
 23:/*      Clock:          C7M (33MHz)                                     */
 24:/*      Unused:         11(I),13(I),14(I/O),15(I/O),16(I/O),19(I/O)     */
 25:/*                                                                      */
 26:/************************************************************************/
 27:/*                                                                      */
 28:/* REVISION HISTORY:                                                    */
 29:/*                                                                      */
 30:/*      DBH Jul  9:     Original version.                               */
 31:/*                                                                      */
 32:/************************************************************************/
 33:
 34:/** INPUTS: **/
 35:
 36:PIN 1           =  C7M          ;       /* Zorro III arbiter clock. */
 37:PIN 2           = !MASTER       ;       /* SCSI owns the A3090 bus. */
 38:PIN 3           = !SBR          ;       /* SCSI bus request. */
 39:PIN 4           = !EBG          ;       /* Expansion bus grant. */
 40:PIN 5           =  FCS          ;       /* Zorro III cycle strobe. */
 41:PIN 6           = !SLAVE        ;       /* Zorro III slave response. */
 42:PIN 7           = !DTACK        ;       /* Zorro III bus termination. */
 43:PIN 8           = !BERR         ;       /* Zorro III bus error. */
 44:PIN 9           = !RST          ;       /* Zorro III reset. */
 45:PIN 10          =  CLK          ;       /* NCR 53C710 bus clock. */
 46:
 47:/** OUTPUTS: **/
 48:
 49:PIN 17          = !MYBUS        ;       /* A3090 owns the Zorro III bus. */
 50:PIN 18          = !SBG          ;       /* SCSI bus grant. */
 51:PIN 20          = !REGED        ;       /* A3090 is registered as a Zorro III master. */
 52:PIN 21          = !EBR          ;       /* Zorro III bus request. */
 53:PIN 23          =  BMASTER      ;       /* Buffered/inverted version of MASTER. */

LISTING FOR LOGIC DESCRIPTION FILE: u303.pld                         Page 2

CUPL: Universal Compiler for Programmable Logic
Version 4.0a Serial# MD-40A-8380
Copyright (C)  1983,1990 Logical Devices, Inc.
Created Fri Jan 04 02:50:57 1980

 54:
 55:/** USED INTERNALLY: **/
 56:
 57:PIN 22          = !RCHNG        ;       /* Registration is changing. */
 58:
 59:/** OUTPUT TERMS: **/
 60:
 61:/* The SCSI chip can be given the A3090 bus as soon as there's no activity on it. 
 62:   Hold onto it until the SCSI becomes master. */
 63:
 64:SBG             = !FCS & !DTACK & !RST & SBR
 65:                #  SBG &  SBR
 66:                #  SBG & !MASTER;
 67:
 68:/* The Zorro III bus request is driven out on C7M high, for one C7M cycle, to
 69:   register for bus mastership.  When done, the same sequence relinquishes
 70:   registration.  The RCHNG signal indicated when a change is necessary. */
 71:
 72:EBR.D           = RCHNG & !EBR & !RST;
 73:EBR.AR          = RST;
 74:
 75:/* A change of registration is necessary whenever a SCSI request comes in 
 76:   and we're unregistered, or when the MASTER line is dropped and we are
 77:   registered. */
 78:
 79:RCNHG           = !REGED & SBR & !EBR
 80:                #  REGED & !MASTER & !EBR;
 81:
 82:/* Here's the actual registration indicator.  We're registered when EBR toggles,
 83:   unregistered the next time it toggles.  This can only change while EBR is low,
 84:   or in response to an error or reset condition. */
 85:
 86:REGED.D         = !REGED & EBR
 87:                #  REGED & !EBR & !RST;
 88:REGED.AR        = RST;
 89:
 90:/* The A3090 has the Zorro III bus only if its registered and it receives a grant.
 91:   It holds the bus until the grant is removed and the cycle ends. */
 92:
 93:MYBUS           = REGED & EBG
 94:                # MYBUS & FCS & !RST;
 95:
 96:
 97:

[0016cb] Please note: no expression assigned to:  EBR.sp
[0016cb] Please note: no expression assigned to:  REGED.sp


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