44801A.txt

PAL16R8
JLB/CJTC 11AUG86
44801A,10D, BARB

OSC /CRQ /IORQ /MR /BRQ50 /REFRQ50 /BDRY25 /SEMRQ50 NC9 GND
/OE /CACT /GNT /IOD /REF /MEM /DOREF /ACT /SEM VCC

; CACT - CPU IS ACTIVE ON THE ND100 BUS

CACT := CRQ * /REFRQ50 * /BRQ50 * /REF * /GNT * /SEM * /BDRY25 * /MR    ; 4
      + CRQ * /REFRQ50 * DOREF  * /REF * /GNT * /SEM * /BDRY25 * /MR    ; 2
      + CACT * /BDRY25 * /MR                                            ; HOLD     
      + CRQ * SEM * /GNT * /BDRY25 * /MR                                ; SEMAPHORE

; REF - REFRESH GRANT ON ND100 BUS

REF := REFRQ50 * /CACT * /GNT * /SEM * /BDRY25                          ; 1
     + REF * /BDRY25                                                    ; HOLD
     + REFRQ50 * MR                                                     ; ALWAYS GRANT REFRESH DURING MR

; GNT - GRANT ND100 BUS TO A DMA DEVICE OR EXTERNAL BUS CONTROLLER

GNT := BRQ50 * /REFRQ50 * /CRQ   * /REF * /CACT * /SEM * /BDRY25 * /MR  ; 3
     + BRQ50 * /REFRQ50 * /DOREF * /REF * /CACT * /SEM * /BDRY25 * /MR  ; 3
     + GNT * /BDRY25 * /MR                                              ; HOLD
     + BRQ50 * SEM * GNT * /MR                                          ; SEMAPHORE

; IOD - IO SIGNAL TO LAST FOR THE ENTIRE BUS CYCLE

IOD := IORQ * CRQ * /REFRQ50 * /BRQSO * /REF * /GNT * /SEM * /BDRY25 * /MR  ; 4
     + IORQ * CRQ * /REFRQSO * DOREF  * /REF * /GNT * /SEM * /BDRY25 * /MR  ; 2
     + IOD * /BDRY25 * /MR                                                  ; HOLD
     + IORQ * CRQ * SEM * /GNT * /BDRY25 * /MR                              ; SEMAPHORE

; MEM - MEM SIGNAL TO LAST FOR ENTIRE BUS CYCLE
; GENERATES BMEM WHICH IS PRESENT ON REFRESH, CPU MEMORY AND DMA CYCLES

MEM := BRQ50   * /IORQ  *  /IOD * /BDRY25 * /MR
     + BRQ50   * /CRQ   *  /IOD * /BDRY25 * /MR
     + BRQ50   * /DOREF *  /IOD * /BDRY25 * /MR
     + CRQ     * /IORQ  *  /IOD * /BDRY25 * /MR
     + REFRQ50 *           /IOD * /BDRY25
     + REFRQ50 * MR
     + MEM * /BDRY25 * /MR
     
; SEM - SEMAPHORE GRANT SIGNAL

SEM := SEMRQ50 * /MR * BDRY25
     + SEM * /MR * /ACT

; ACT - BUS IS ACTIVE

ACT := CACT * /BDRY25 * /MR
     + GNT  * /BDRY25 * /MR
     + REF  * /BDRY25 * /MR

; DOREF - INDICATES THAT LAST BUS CYCLE WAS A REFRESH

DOREF := REF * /MR * BDRY25
       + DOREF * /MR * /CACT * /GNT * /REF

DESCRIPTION

; PRIORITY:
;           1. REFRESH
:           2. CPU REQUEST AFTER A REFRESH
;           3. BUS REQUEST
;           4. CPU REQUEST

; 26/2-87JLB: WRONG HOLD TERM IN IOD.
;
; 180587 M3202B