Club Amiga de Montreal - CAM/CAM_CD_1.iso/files/373.lha/Sim_v4.2/english.docs/xdc.doc.pp/xdc.doc

Text File | 1990-02-12 | 12.8 KB | 535 lines

            XDC - External Device Compiler - and
            DDL - Device Definition Language




      Contents:


      1  Introduction:

      2  External Devices
      2.1  Combinatorial circuits
      2.2  Asynchronous sequential logic systems
      2.3  Synchronous sequential logic systems

      3  Description of XDC and DDL
      3.1  Call of XDC
      3.2  Syntax of DDL
         3.2.1  Keywords
         3.2.2  Syntaxdiagrams

      4  Error messages

      5  Acknowledgements





      1  Introduction:


      XDC and DDL allow to define external devices for the register trans-
      fer net simulator Sim (V4.0 and higher). With XDC it is possible to
      increase the number of devices that can be simulated. It is also pos-
      sible to increase the speed of the simulation if parts of a register
      transfer net are combined in new, complexer components. New devices
      can be combinatorial circuits, asynchronous, and synchronous sequen-
      tial logic systems.





      2  External Devices

      Fundamental it is possible to define any given device. With synchro-
      nous sequential logic systems it is necessary to consider the sequen-
      tial handling of the devices (see 2.3).



      2.1  Combinatorial circuits


      Example of an AND device with four inputs:

         device x_and;

         input  in1,in2,in3,in4;
         output out;

         {
            out = in1 & in2 & in3 & in4;
         }



      2.2  Asynchronous sequential logic systems


      Example of an asynchronous automat:

         Automat graph:

                    ___                   ___
              +--- /   \       1/0       /   \ ---+
          0/0 |    | 0 | --------------> | 1 |    | 1/0
              +--> \___/                 \___/ <--+

                     A                     |
                     |                     |
                 0/0 |                     | 0/0
                     |                     |
                     |                     V
                    ___                   ___
              +--- /   \       1/1       /   \ ---+
          1/1 |    | 3 | <-------------- | 2 |    | 0/0
              +--> \___/                 \___/ <--+


         Definition:


         device auto;

         input  in;
         output out;
         state  s;

         {
            switch (s) {
             case 0:
               if (in & 1)
                  s = 1;
               break;
             case 1:
               if (~in & 1)
                  s = 2;
               break;
             case 2:
               if (in & 1) {
                  s = 3;
                  out = 1;
               }
               break;
             case 3:
               if (~in & 1) {
                  s = 0;
                  out = 0;
               }
               break;
            }
         }



      2.3  Synchronous sequential logic systems


      With sysnchronous sequential logic systems the value of the input
      leads have to be buffered. Due to the forced sequencing of the devices
      the input values must not be assigned directly to the outputs. If this
      is done, a second register that is connected to the output of the first
      will read the new but wrong value.

      Example of a positive-edge-triggered D-Register:

         device x_reg;
         input  c,d;
         output q;
         state  s;

         {
            if (c & 1)
               q = s;
            else
               s = d;
         }





      3  Description of XDC and DDL


      XDC transforms the device definition to C source code which must be
      compiled afterwards. Up to now only the AZTEC compiler is tested.
      Generally spoken, the compiler must generate code using 16-bit-
      integers with LARGE DATE (AZTEC: +D) memory model. For the LATTICE
      compiler the file xcomp have to be changed.



      3.1  Call of XDC


      For the usage of XDC a AZTEC compiler and linker is needed. The direc-
      tory, in which XDC lies, must contain the following files:

         xcomp, sim.h, sim_msg.h

      XDC is started by the following statement:

         Execute xcomp <device>

      The file, containing the device definition, must have the name
      <device>.x. .x must not be given on the call of xcomp.

      xcomp generates a file <device>. This file is the new external device.
      This means this new device can be used in a VLI. The input and output
      lead name have to be given in the sequence of their definition in
      <device>.x. The file <device> should be copied to the directory that
      contains the simulator.



      3.2  Syntax of DDL
      3.2.1  Keywords


      The DDL uses the following keywords:

         BREAK    CASE     DEFAULT  DEVICE   ELSE
         IF       INPUT    OUTPUT   STATE    SWITCH

      The keyword can be written in capitals or non-capitals (also mixed).



      3.2.2  Syntaxdiagrams


      file:

      --> device_definition -->


      device_definition:

      --> DEVICE --> identifier --> ';' --> declaration_list --+
                                                               |
          +------------------------<---------------------------+
          |
          +--> '{' --> statement_list --> '}' -->


      comment:

      --> '/*' ---+----------------+--> '*/' -->
                  A                |
                  +-- character <--+


      declaration_list:

      --> input_declaration_list --> output_declaration_list --+
                                                               |
          +-------------------------<--------------------------+
          |
          +--> state_declaration_list --+-->
          |                             A
          +--------------->-------------+


      input_declaration_list:

      --+--> input_declaration --+-->
        A                        |
        +------------<-----------+


      input_declaration:

      --> INPUT --> identifier_list --> ';' -->


      output_declaration_list:

      --+--> output_declaration --+-->
        A                         |
        +-------------<-----------+


      output_declaration:

      --> OUTPUT --> identifier_list --> ';' -->


      state_declaration_list:

      --+--> state_declaration --+-->
        A                        |
        +------------<-----------+


      state_declaration:

      --> STATE --> identifier_list --> ';' -->


      identifier_list:

      --+--> identifier --+-->
        A                 |
        +------ ',' <-----+


      identifier:

      --> letter --+------->------+-->
                   A              |
                   +<-- letter <--+
                   |              |
                   +---- digit <--+


      letter:

      --+--> 'A' ---+-->
        |     .     A
        |     .     |
        |           |
        +--> 'Z' -->+
        |           |
        +--> 'a' -->+
        |     .     |
        |     .     |
        |           |
        +--> 'z' -->+
        |           |
        +--> '_' ---+


      digit:

      --+--> '0' --+-->
        |     .    A
        |     .    |
        |          |
        +--> '9' --+


      statement_list:

      --+--> statement --+-->
        A                |
        +--------<-------+


      statement:

      --+--> switch_statement ------>+-->
        |                            A
        +--> if_statement ---------->+
        |                            |
        +--> assignment_statement -->+
        |                            |
        +----------> ';' ------------+


      assignment_statement:

      --> identifier --> '=' --> expression --> ';' -->


      expression:

      --+--> expression -------------------------------+-->
        |                                              A
        +--> '~' --> expression ---------------------->+
        |                                              |
        +--> constant -------------------------------->+
        |                                              |
        +--> identifier ------------------------------>+
        |                                              |
        +--> '(' --> expression --> ')' -------------->+
        |                                              |
        +--> expression --> operator --> expression ---+


      operator:

      --+--> '>' --->+-->
        |            A
        +--> '<' --->+
        |            |
        +--> '>=' -->+
        |            |
        +--> '<=' -->+
        |            |
        +--> '==' -->+
        |            |
        +--> '!=' -->+
        |            |
        +--> '&' --->+
        |            |
        +--> '|' --->+
        |            |
        +--> '^' --->+
        |            |
        +--> '+' --->+
        |            |
        +--> '-' --->+
        |            |
        +--> '>>' -->+
        |            |
        +--> '<<' ---+


      if_statement:

      --> IF --> '(' --> expression --> ')' --> if_else_statement_list--+
                                                                        |
          +-----------------------------<-------------------------------+
          |
          +--> ELSE --> if_else_statement --+-->
          |                                 A
          +----------------->---------------+


      if_else_statement_list:

      --+--> statement -----------------------+-->
        |                                     A
        +--> '{' --> statement_list --> '}' --+


      switch_statement:

      --> SWITCH --> '(' --> expression --> ')' --> switch_statement_list -->


      switch_statement_list:

      --> '{' --+--> case_statment --+---+--> default_statement --+--> '}' -->
                A                    |   |                        A
                +----------<---------+   +------------>-----------+


      case_statement:

      --> CASE --> constant --> ':' --+--> statement_list --+--+
                                      |                     A  |
                                      +---------->----------+  |
                                                               |
          +--------------------------<-------------------------+
          |
          +--> BREAK --> ';' --+-->
          |                    A
          +--------------------+


      default_statement:

      --> DEFAULT --> ':' --+--> statement_list --+---+--> BREAK --+-->
                            |                     A   |            A
                            +---------->----------+   +------>-----+


      constant:

      --+--> hexadecimal_constant --+-->
        |                           A
        +--> decimal_constant-------+


      hexadecimal_constant:

                        +----------<---------+
                        V                    |
      --+--> '0x' --+---+---+--> digit --+---+-->
        |           A       |            A
        +--> '0X' --+       +--> 'A' --->+
                            |     .      |
                            |     .      |
                            |            |
                            +--> 'F' --->+
                            |            |
                            +--> 'a' --->+
                            |     .      |
                            |     .      |
                            |            |
                            +--> 'f' ----+


      decimal_constant:

      --+--> '0' -----------------------------+-->
        |                                     A
        +--> positive_digit --+--> digit --+--+
                              A            |
                              +------<-----+


      positive_digit:

      --+--> '1' --+-->
        |     .    A
        |     .    |
        |          |
        +--> '9' --+





      4  Error messages


      There are three classes of errors:

         a) parse errors without description


         b) parse errors with description

            '=' expected
            '(' expected
            ')' expected
            '{' expected
            '}' expected
            ';' expected
            ':' expected
            constant expected
            lead name expected


         c) semantical errors

            BREAK outside of SWITCH
            CASE outside of SWITCH
            DEFAULT outside of SWITCH
            no CASE behind DEFAULT
            missing CASE
            duplicate CASE
            duplicate DEFAULT
            already defined lead name
            undefined lead
            device name differs from file name
            no memory


      Error should be corrected from the start to the end because there are
      often succeeding errors. Succeeding error occur mostly with the clas-
      ses a) and b), seldom with c).





      5  Acknowledgements


      Sim, XDC, and DDL owe to Klaus-Dieter Renner whose idea and design of
      a register transfer net simulator and a device definition language
      gives the stimulation for my programs, and to Michael Koch for beta-
      testing and his suggestions of new features.