mem dram ckt1

;PALASM Design Description

;---------------------------------- Declaration Segment ------------
TITLE    SAMPLE Z80 DESIGN # 1 SYSTEM TIMING CONTROLLER
PATTERN  Z80-1
REVISION A
AUTHOR   TIM OLMSTEAD
COMPANY  
DATE     09/20/96

CHIP  PAL1  PAL16L8

;---------------------------------- PIN Declarations ---------------
PIN  1          MREQ                            ; INPUT 
PIN  2          CASIN                           ; INPUT 
PIN  3          A07                             ; INPUT 
PIN  4          A06                             ; INPUT 
PIN  5          RD                              ; INPUT 
PIN  6          IORQ                            ; INPUT 
PIN  7          M1                              ; INPUT 
PIN  8          RFSH                            ; INPUT 
PIN  9          WR                              ; INPUT 
PIN  10         GND                             ; INPUT 
PIN  11         PIN11                           ; INPUT 
PIN  12         CAS                  COMBINATORIAL ; OUTPUT
PIN  13         RAS                  COMBINATORIAL ; OUTPUT
PIN  14         STARTUP                         ; INPUT 
PIN  15         PIN15                           ; INPUT 
PIN  16         CTC                  COMBINATORIAL ; OUTPUT
PIN  17         SIO                  COMBINATORIAL ; OUTPUT
PIN  18         ROM                  COMBINATORIAL ; OUTPUT
PIN  19         RAMSEL               COMBINATORIAL ; OUTPUT
PIN  20         VCC                             ; INPUT 

;----------------------------------- Boolean Equation Segment ------
EQUATIONS

/RAMSEL = /MREQ * RFSH           ; THE WHOLE 64K IS DRAM
        + /MREQ * /RFSH          ; REFRESH

/ROM = STARTUP * /MREQ * /RD     ; ROM IS ONLY ENABLED DURING STARTUP


/RAS = /MREQ * STARTUP * /WR * RFSH ; ONLY DO WRITES DURING STARTUP
     + /MREQ * /STARTUP * RFSH   ; ALL ACCESSES AFTER STARTUP
     + /MREQ * /RFSH * /CASIN    ; REFRESH

/CAS = RFSH * /CASIN * /RD * /STARTUP ; NORMAL CAS FOR MEMORY READ AFTER
                                      ; STARTUP
     + RFSH * /CASIN * /WR       ; HOLD OFF CAS FOR EARLY WRITES
     + /RFSH * /MREQ             ; CAS GOES LOW EARLY FOR REFRESH

/SIO = /IORQ * M1 * /A07 * /A06  ; SIO AT 00H


/CTC = /IORQ * M1 * /A07 * A06   ; CTC AT 40H

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