rfc186.txt

著名的RFC文档,其中有一些文档是已经翻译成中文的的.

   If no SETUP request has previously been executed error condition 1 is
   recognized.

   If A1 is negative or if A2 is less than the origin of the display
   program, error condition 2 is recognized.

   If A1 + A2 is greater than the end of the display program, then the
   length of the display program is increased to equal "A1 + A2 -
   origin".  The WAR area remains the same length as before, and its
   contents are shifted to their new locations.  The "effective WAR
   value" (see TRANSMIT) is increased by the amount of increase in
   display program length.















Michener                                                        [Page 9]

RFC 186                A Network Graphics Loader            12 July 1971


   An acknowledge message is sent (unless suppressed) if no error
   condition is recognized (and if no problem with core size limitation
   arises).  Also, the flag which is set by severe error conditions
   encountered during EXECUTE requests, is cleared by successful UPDATE
   requests.

   The next "A1" words are read and stored in consecutive locations
   starting in location "A2".  If A1 is zero, no words are read.

   If the mode field of the first word of the UPDATE request is
   positive, it is taken as an iteration count for a multiple EXECUTE
   request.  Otherwise, the next request is read from the Network.

5.  The FLUSH request.

   The Flush request takes no arguments and ignores the mode field of
   the first word of the request.  No acknowledge message is sent.  The
   network connection is broken and the process destroys itself.

6.  THE MODESET request.

   The mode field of the first request word is decoded first.  If it is
   zero or less, or if it is greater than (currently) 6, error condition
   2 is recognized.

   6A.   If the mode field is 1, then acknowledge messages and ASCII
         error messages are not to be suppressed.

   6B.   If the mode field is 2, then acknowledge messages and ASCII
         error messages are to be suppressed.

   6C.   If the mode field is 3, exit from Auto TRANSMIT mode.  (See
         6D.)

   6D.   If the mode field is 4 or 5, whenever an EXECUTE has a normal
         stop, a TRANSMIT request is to be automatically performed.

   The mode field for the transmit is to be 4 less than the mode field
   for this MODESET request.  One (more) word is read from the network.
   It contains the arguments for the TRANSMIT.  (That is, the word is
   saved and used when the TRANSMIT operation is performed.  The values
   of the arguments are checked at that time, not during the MODESET
   request.








Michener                                                       [Page 10]

RFC 186                A Network Graphics Loader            12 July 1971


EXAMPLE

   Suppose a display routine calculated and saved a different 3
   dimensional transformation matrix each time it was executed.  (It
   might be programmed to make an object appear to rotate.)  The user of
   the routine typically would want to set up the matrices and then "let
   'er rip" with ten or twenty (or more) executions.  This could be done
   as follows:

        SETUP,,0

    +-->length,,2000          ; length of display pgm
    |    -                    ; large output area
    |   |  -----
    |   |  -----
    +-->   -----
        | program
        |  -----
        |  -----
         -

        MODESET,,5            ; auto transmit in ARDS mode

        0,,1000+length        ; arguments for transmit

                              ;    meaning "current contents

                              ;    of output area"

        EXQ,,10               ; execute 10 times, sending

                              ;    the data each time

        UPDATE,,20            ; update, then execute 20 times

        8,,address of matrix  ; arguments for update, to

             -                ;    change a matrix
            |
   8 words -  new matrix
            |
             _
           etc.








Michener                                                       [Page 11]

RFC 186                A Network Graphics Loader            12 July 1971


   The output from the Graphics Loader for this example would be as
   follows:

   ACKNOWLEDGE     setup,setup     :(See description of ACKN

                                   ;  for format in word)

   ACKNOWLEDGE     modeset,modeset

   ACKNOWLEDGE     transmit, exq

        output,,1                   ; output in ARDS mode

        leng1,,0
       _
      |
     -  data
      |_

   ACKNOWLEDGE     transmit,exq

        output,,1

        leng2,,0
       _
      |
     -  data
      |_
             .               (in total, there are 10 sets of output.)
             .
             .

   ACKNOWLEDGE     update,update

   ACKNOWLEDGE     transmit, update

        output,,1

        leng11,,0












Michener                                                       [Page 12]

RFC 186                A Network Graphics Loader            12 July 1971


       -
      |
     -  data
      |
       -
             .
             .               (in total, there are 20 sets of output.)
             .

ACKNOWLEDGE MESSAGES

   These messages are each a single 36 bit word.  They can be suppressed
   dynamically by the MODESET request.  The left half of the 36 bit word
   identifies the fact that it is an acknowledge message by containing a
   1.  The right half is further divided into two 9-bit fields
   (quarters).  The right 9-bit field (within the right half word)
   contains the opcode field of the last request sent by the user.  Thus
   if an UPDATE request was received last, this field is a 4.

   The left 9-bit field (within the right half word) contains the number
   of the action actually being performed.  This differs from the opcode
   of the last request received only for Auto TRANSMIT mode and when a
   positive mode field is given in an UPDATE request (which is an
   EXECUTE count).

   Possible pairs of these fields are given below.  Note that Auto
   TRANSMIT mode sends only one acknowledge message which indicates both
   successful execution of the display program _and_ correct parameters
   for the TRANSMIT operation.






















Michener                                                       [Page 13]

RFC 186                A Network Graphics Loader            12 July 1971


   Currently    Most Recent    Comments:
   Executing:   Request
                Received:

   SETUP        SETUP           ; Sent before data words are read.

   EXQ          EXQ             ; Never sent in Auto-Transmit mode.

   TRANSMIT     EXQ              ; Only sent in Auto-Transmit mode.

   TRANSMIT     TRANSMIT

   EXQ          UPDATE          ; Never sent in Auto-Transmit mode.

   TRANSMIT     UPDATE          ; Only sent in Auto-Transmit mode.

   UPDATE       UPDATE          ; Sent before data words are read.

   MODESET      MODESET         ; When setting up Auto-Transmit mode,

                                ;   this is sent before the argument

                                ;   word for TRANSMIT is read.

Notes:

   1)    A MODESET request which suppresses acknowledge messages is
         never acknowledged.  One which permits acknowledge messages is
         always acknowledged.

   2)    Requests which read data words (certain SETUP, UPDATE and
         MODESET requests) send acknowledge messages (unless suppressed)
         _before_ reading the data words.

ERROR MESSAGES

   These messages contain one or more words.  If acknowledge messages
   are suppressed, then only one word is sent.  (The assumption was made
   that brevity of response would also be desired for error messages if
   it were also desired for normal output.)

   The first (or only) word contains a left half of 2.  (Identifying
   this as an error message).  The right half contains the number of the
   error condition recognized; these numbers are summarized below.

   If the long form of the error message is being used, additional words
   are sent, the first contains a positive count of the remaining words
   in the left half and zero in the right half.  Words following the



Michener                                                       [Page 14]

RFC 186                A Network Graphics Loader            12 July 1971


   count word contain five 7-bit ASCII characters per word (the last
   word may end in null characters) which spell out a descriptive error
   message.  These messages are summarized below:

   Error Condition Number          Error Message

             0              UNRECOGNIZED OPERATION CODE

             1              PREVIOUS SETUP REQUIRED

             2              INVALID MODE OR OPERAND FIELD

             3              PREVIOUS EXECUTE FAILED

             4              DISPLAY PROCESSOR OCCUPIED

             5              OUTPUT AREA OVERRUN

             6              DISPLAY ERROR: TWO SECOND TIME OUT

             7              DISPLAY ERROR: IMPROPER DISPLAY STOP

             8              DISPLAY ERROR: MEMORY PROTECTION VIOLATION

OUTPUT FROM TRANSMIT

   This output consists of an identifying word (left half of 3, right
   half containing 0 for image mode and 1 for ARDS mode), a count word
   (left half indicating the number of words following this word, right
   half of zero) and zero or more data words in whatever data format the
   first word indicated.




















Michener                                                       [Page 15]

RFC 186                A Network Graphics Loader            12 July 1971


Appendix 1

   The environment at the beginning of execution of the user's display
   program is as follows:

This LDS-1 is in program mode.

RAR/                    Origin of user's program.

WAR/                    First word of a block of core at least as long
                        as requested via SETUP operations.  This block
                        immediately follows the last word of the display
                        program.

PC/                     Origin of user's program.

SP/                     Address of first word beyond the end of a 200
                        (octal) word area of combined data sink and
                        control register stack.

P1/                     Unspecified.

P2/                     Unspecified.

DSP/                    First word of a 200 (octal) word area of
                        combined data sink and control register stack.

UR/                     Unspecified.

RCR/                    Unspecified.

WCR/                    Minus one plus the negative of the length of the
                        "WAR area" as specified in the most recent
                        SETUP request.

DIR/                    Stop on WCR positive.
                        Do not stop on Hit.
                        Matrix Multiplier inactive.
                        "Overlap" permitted.
                        Two dimensional mode.
                        Do not "Do Twice".

RSR/                    Unspecified.

SR/                     0, except for bits not under program control
                        like the stylus "Z" coordinate bits.

NEXT/                   Unspecified.



Michener                                                       [Page 16]

RFC 186                A Network Graphics Loader            12 July 1971


SAVELB/                 -3777,,-3777

SAVERT/                 3777,,3777

VIEWLB/                 -3777,,-3777

VIEWRT/                 3777,,3777

WINDLB/                 -3777,,-3777

WINDRT/                 3777,,3777

INSTLB/                 -3777,,-3777

INSTRT/                 3777,,3777

NAME/                   Unspecified.

CDIR/                   Scaled Coordinates to Memory
                        Curve mode inactive.
                        Minimum effort inactive.
                        Solid, not dashed lines.
                        Self mode inactive.

HITANG/                 Unspecified.

SELINT/                 Unspecified.

Matrix Multiplier/      Unspecified.

Origin of program -1/           (Should be jumped to when the
                                 display program is finished.)


        [This RFC was put into machine readable form for entry]
         [into the online RFC archives by Lorrie Shiota, 10/01]















Michener                                                       [Page 17]