Name      23007C6;

Assembly  0001;
Revision  1.0;
PartNo    E14 82S100;
Device    f1508ispplcc84;

Company   None;
Designer  Digital Equipment Corporation;
Location  None;
Date      March 2018;

property ATMEL { jtag=on };
PROPERTY ATMEL { preassign keep };
PROPERTY ATMEL { TMS_pullup=on };
PROPERTY ATMEL { TDI_pullup=on };
/* PROPERTY ATMEL { pin_keep OFF }; */
/* PROPERTY ATMEL { open_collector = INT_RQST }; */

/*
 * 23007C6 is an 82S100, programmed to partially decode IOT instructions for the KT8-A.
 * An 82S100 has 16 dedicated inputs, and 8 dedicated outputs.  In this case, the inputs
 * are a copy of the instruction on BM[1..11], and the control signals DIOI, USM, EEM, 
 * and RVFEN.  BPAUSE acts an enable, preventing decoding for non-IOT instructions.  The
 * outputs are a control signal indicating to drive the bus during TS3: C0, C1, !HOS, 
 * !C17EN, !CFROM, !DECEN, and !INIOEN.
 *
 * Instructions with EEM clear:
 * 110 000 000 100 GTF c0 c1 drive
 * 110 000 000 101 RTF c0
 * 110 010 000 000 LXM c0 (KT8-A only)
 * 110 010 000 100 CINT
 * 110 010 001 100 RDF drive
 * 110 010 010 100 RIF drive
 * 110 010 011 100 RIB drive
 * 110 010 100 100 RMF
 * 110 010 101 100 SINT
 * 110 010 110 100 CUF
 * 110 010 111 100 SUF
 * 110 010 xxx 001 CDF
 * 110 010 xxx 010 CIF
 * 110 010 xxx 011 CIF CDF
 *
 * Instructions for memory boards:
 * 110 001 000 001 SBE*
 * 110 001 000 010 SPL*
 * 110 001 000 011 CAL*
 *
 * Additional instructions with EEM set:
 * 110 001 111 000 LBM c0
 * 110 001 111 001 RBM drive
 * 110 001 111 010 RLB c0 c1 drive
 * 110 001 111 011 RMR c0 c1 drive
 * 110 001 111 100 MBC c0
 * 110 001 111 101 RACA c0 c1 drive
 * 110 001 111 110 RACB c0 c1 drive
 * 110 001 111 111 RACC c0 c1 drive
 * 110 01x nnn y01 CDF
 * 110 01x nnn y10 CIF
 * 110 01x nnn y11 CIF CDF
 * 110 010 001 000 GTS c0 c1 drive
 * 110 010 010 000 RTS c0
 * 110 010 011 000 RXM c0 c1 drive
 * 110 010 100 000 LRR c0
 * 110 010 101 000 RRR c0 c1 drive
 * 110 010 110 000 LUSR c0
 * 110 010 111 000 RUSR c0 drive
 * 110 001 000 001 SBE*
 * 110 001 000 010 SPL*
 * 110 001 000 011 CAL*
 *
 * N.B.  The extensions are incompatible with Posibus/Negibus machines, 
 * which do not support 6xx0 IOTs, including LXM.  (On such a machine, 
 * this will always emulate the standard MMU.)
*/

Pin 19 = !CE;
/*
 * What we are calling BM1 here actually is the product of FETCH, BM0, and BM1 from the CPU.
*/
Pin 20 = BM1;
/*
 * These are just bits of the instruction, as presented on the memory bus.
*/
Pin [21..27,2..4] = [BM2..11];
/*
 * PAUSE is asserted during the execution of IOT instructions.
*/
Pin  5 = PAUSE;
/*
 * RVFEN enables virtual fields in user mode.  That is, RIF and RDF
 * will not trap.
*/
Pin  6 = RVFEN;
/*
 * EEM is set when the full KT8-A instruction set is enabled.
*/
Pin  7 = EEM;
/*
 * USM is set if we are currently in user mode.
*/
Pin  8 = USM;
/*
 * DIOI disables trapping on I/O instructions in user mode, 
 * except CIF and CDF to fields outside the user limit.
*/
Pin  9 = DIOI;

/* Outputs */
Pin 10 = inioen;
Pin 11 = !decen;
Pin 12 = !cfrom;
Pin 13 = !c17en;
Pin 15 = !hos;
Pin 16 = c0;
Pin 17 = c1;
Pin 18 = drive;

/*
 * Normally PAUSE would indicate an IOT in progress, but PAUSE 
 * is suppressed by USM (except for LET_IO cases).  We check for 
 * the case that user mode IOTs are generally enabled (DIOI) here.
*/
IOT = PAUSE
    # USM & DIOI & BM1 & !BM2;

/*
 * INIOEN is used to gate LXM, GTF, and RTF IOTs.
*/
inioen = IOT & !USM & !BM3 & !BM5 & !BM6 & !BM7 & !BM8 & !BM10;

/*
 * DECEN is used to gate IOTs that don't change field.
*/
decen = IOT & !USM & !BM3 & BM4 & !BM10 & !BM11; /* 110 01x xxx x00 */

/*
 * CFROM is used to gate the change field decode ROM, E28.
*/
cfrom = IOT &       !BM3 & BM4 & !BM5 & !BM9 & (BM10 # BM11)  /* CIF, CDF */
      # IOT & EEM & !BM3 & BM4 &               (BM10 # BM11); /* CIF, CDF */

/*
 * C17EN is used to gate the C17 ROM.
*/
c17en = IOT & EEM & !BM3 & !BM4 & BM5 & BM6 & BM7 & BM8;

/*
 * HOS is asserted during the fetch of HLT or OSR in user mode.
*/
hos = USM & BM1 & BM2 & BM3 & (BM9 # BM10) & !BM11;

/*
 * C0 is used to indicate that the processor should transfer the 
 * contents of the DATA bus to or from the AC, rather than OR it.
 *
 * Instructions with c0 asserted:
 * 110 000 000 100 GTF c0 c1 drive
 * 110 000 000 101 RTF c0
 * 110 001 111 000 LBM c0
 * 110 001 111 010 RLB c0 c1 drive
 * 110 001 111 011 RMR c0 c1 drive
 * 110 001 111 100 MBC c0
 * 110 001 111 101 RACA c0 c1 drive
 * 110 001 111 110 RACB c0 c1 drive
 * 110 001 111 111 RACC c0 c1 drive
 * 110 010 000 000 LXM c0 (KT8-A only)
 * 110 010 001 000 GTS c0 c1 drive
 * 110 010 010 000 RTS c0
 * 110 010 011 000 RXM c0 c1 drive
 * 110 010 100 000 LRR c0
 * 110 010 101 000 RRR c0 c1 drive
 * 110 010 110 000 LUSR c0
 * 110 010 111 000 RUSR c0 drive
*/
BM3_10_00000010 = !BM3 & !BM4 & !BM5 & !BM6 & !BM7 & !BM8 &  BM9 & !BM10;
c0 = IOT &        BM3_10_00000010
   # IOT & EEM & !BM3 & !BM4 &  BM5 & BM6 & BM7 & BM8 & !(!BM9 & !BM10 & BM11)
   # IOT & EEM & !BM3 &  BM4 & !BM5 &                     !BM9 & !BM10 & !BM11;

/*
 * C1 is used with C0 active to indicate the I/O direction and 
 * whether the AC should should be cleared.  (Active loads AC, 
 * inactive writes device, then clears AC.)  Ignored unless C0 
 * is active.
 *
 * Instructions with C1 asserted:
 * 110 000 000 100 GTF c0 c1 drive
 * 110 001 111 010 RLB c0 c1 drive
 * 110 001 111 011 RMR c0 c1 drive
 * 110 001 111 101 RACA c0 c1 drive
 * 110 001 111 110 RACB c0 c1 drive
 * 110 001 111 111 RACC c0 c1 drive
 * 110 010 001 000 GTS c0 c1 drive
 * 110 010 011 000 RXM c0 c1 drive
 * 110 010 101 000 RRR c0 c1 drive
*/
BM3_11_000000100 = !BM3 & !BM4 & !BM5 & !BM6 & !BM7 & !BM8 &  BM9 & !BM10 & !BM11;
BM3_11_001111x1x = !BM3 & !BM4 &  BM5 &  BM6 &  BM7 &  BM8 &         BM10;
BM3_11_001111101 = !BM3 & !BM4 &  BM5 &  BM6 &  BM7 &  BM8 &  BM9 & !BM10 &  BM11;
BM3_11_0100x1000 = !BM3 &  BM4 & !BM5 & !BM6 &         BM8 & !BM9 & !BM10 & !BM11;
BM3_11_010101000 = !BM3 &  BM4 & !BM5 &  BM6 & !BM7 &  BM8 & !BM9 & !BM10 & !BM11;
c1 = IOT &       BM3_11_000000100
   # IOT & EEM & BM3_11_001111x1x
   # IOT & EEM & BM3_11_001111101
   # IOT & EEM & BM3_11_0100x1000
   # IOT & EEM & BM3_11_010101000;

/*
 * DRIVE is used to indicate that the data bus should be driven.
 *
 * Instructions with DRIVE asserted:
 * 110 000 000 100 GTF c0 c1 drive
 * 110 001 111 001 RBM drive
 * 110 001 111 010 RLB c0 c1 drive
 * 110 001 111 011 RMR c0 c1 drive
 * 110 001 111 101 RACA c0 c1 drive
 * 110 001 111 110 RACB c0 c1 drive
 * 110 001 111 111 RACC c0 c1 drive
 * 110 010 001 000 GTS c0 c1 drive
 * 110 010 001 100 RDF drive
 * 110 010 010 100 RIF drive
 * 110 010 011 000 RXM c0 c1 drive
 * 110 010 011 100 RIB drive
 * 110 010 101 000 RRR c0 c1 drive
 * 110 010 111 000 RUSR c0 drive
*/
BM3_11_010001100 = !BM3 & BM4 & !BM5 & !BM6 & !BM7 &  BM8 &  BM9 & !BM10 & !BM11;
BM3_11_01001x100 = !BM3 & BM4 & !BM5 & !BM6 &  BM7 &         BM9 & !BM10 & !BM11;
BM3_11_010xx1000 = !BM3 & BM4 & !BM5 &                BM8 & !BM9 & !BM10 & !BM11;
drive = IOT &       BM3_11_000000100
      # IOT &       BM3_11_010001100
      # IOT &       BM3_11_01001x100
      # IOT & EEM & BM3_11_010xx1000;

/*
 * CE is implemented here.
*/
inioen.oe = CE;
decen.oe = CE;
cfrom.oe = CE;
c17en.oe = CE;
hos.oe = CE;
c0.oe = CE;
c1.oe = CE;
drive.oe = CE;