iodecode.pld

GAL编译工具(Atmel提供)

Name            Iodecode;
Partno          CA0010;
Revision        02;
Date            9/22/84;
Designer        Osann/Kahl;
Company         Assisted Technology, Inc.;
Assembly        PC Multi-Function;
Location        U12;
Device          G20V8ALCC;

/************************************************************************/
/* This device generates the chip select signals for the I/O functions. */
/* It also enables the data bus transceiver for both memory and I/O     */
/* write cycles.                                                        */
/************************************************************************/

/** Inputs **/

pin [2..7,9,10] = [a9..2] ;                  /* system addresses a2 - a9     */
pin 11     = !memw ;                    /* memory write strobe          */
pin 12     = !iow ;                     /* i/o write strobe             */
pin 13     = !ioacc_in ;                /* same signal as ioacc         */
pin 16     = !memacc ;                  /* on-board memory access       */

/** Outputs **/

pin 18     = !ioacc ;                   /* on-board I/O being accessed  */
pin 19     = !parport ;                 /* parallel port chip select    */
pin 20     = !rtclk ;                   /* real-time clock chip select  */
pin 21     = !serport2 ;                /* serial port #2 chip select   */
pin 23     = !serport1 ;                /* serial port #1 chip select   */
pin 24     = !wrbuff ;                  /* xceiver enable - write cycle */

/** Declarations and Intermediate Variable Definitions  **/

field   ioaddr    = [a9..2] ;
serport1_eqn      = ioaddr:[2F8..2FF] ;  /*******************************/
serport2_eqn      = ioaddr:[3F8..3FF] ;  /*          I/O Address        */
rtclk_eqn         = ioaddr:[100..11F] ;  /*             Ranges          */
parport_eqn       = ioaddr:[1F4..1F7] ;  /*******************************/

/** Logic Equations **/

wrbuff            = memacc & memw # ioacc_in & iow ;
ioacc             = serport1_eqn # serport2_eqn # rtclk_eqn #
                    parport_eqn ;
serport1          = serport1_eqn ;
serport2          = serport2_eqn ;
rtclk             = rtclk_eqn ;
parport           = parport_eqn ;