crc.doc

一个C style Assembler的source code

CRC / 9-bit RS-232, RS-422, RS-485 demo:
   This is a demo illustrating (1) 8-bit CRC check sums, (2) 57600,N,9,1
communications, and (3) RS-422/RS-485 communications.

   crc.asm ... A program that prints out an Intel Hex Format dump of addresses
               0 to 1fffh in code space.  However, instead of calculating check
               sums by adding all the bytes on each line, as is done with Intel
               Hex Format, an 8-bit CRC is produced.
               This also demonstrates communications at 57600 baud using 9 bit
               addressing.  The serial address in this program is ':'.  Every
               key except 's' is echoed.  A hex dump, as described above, is
               sent when 's' is received.  Responses will only be produced
               when the address received exactly matches ':'.
    crc.c .... A C program that will read an CRC-modified intel hex file and
               verify it.
  sample.hex.. A sample hex file.
client/demo.c  A 57600,N,9,1 demonstration client.  This client will work on
               RS-232, RS-422, and RS-485.

The CRC polynomial used by both programs is:

                   x^8 + x^6 + x^5 + x^3 + x^2 + x^0.

   The following assumptions are made about RS-485 links:

       * The T0 line enables the transmit driver at the 8051 when it is set,
         and disables the driver when cleared.

       * OUT1 of the Modem Control Register similarily drives the TX enable
         line on the PC host's RS-485 communications card.