DDP.DOC

DJOE Data Protocol


DDP is used to exchange machine language programs between
computers. Specifications :

Communication is done serial with RS232 levels,1200 bauds,
8 bits, low bit first, no parity, 2 stopbits.


+--
|   16 byte name in ascii, b7=0.
|
|   2 byte load address (note 1), lsb first.
|
|   2 byte length (note 2) of total data, lsb first.
|
+-> CRC (note 3)

    256 bytes of 0FFH


+--                                             --+
|   03AH (= start of block)                       | Repeat if
|                                                 | neccessary
|   1 byte, length of this block (note 4).        |
|                                                 |
|   data                                          |
|                                                 |
+-> CRC (note 3) (2A not included)              --+


    02AH (= end of transmission)




(note 1) The load address is intended as a hint where to load
         the program, but may be overridden by the receiver.

(note 2) For reference only, not to be used to determine
         transmission end.

(note 3) CRC is two bytes, lsb first.
         The lined parts count in CRC.
	 Starting CRC is 0000.

	 CRC  = (CRC    + Byte-to-send) Rotated left on bit.
	    n       n+1

	 The CRC itself is not counted in the CRC.

(note 4) 00 means 256 bytes long.