Working protocol : (for transferring one prog)

Transmitter		Receiver		Notes
			
Sends byte 22		
			Sends byte 19
Sends bytes:58,80,c,0,				Things get complicated here.
a,b,0,0,(255;31 of),x				c=49+program memory number
						a=high byte of prog. length
						b=low byte of prog. length
						x=checksum, fix this byte so that the low byte
						of (the sum of all the bytes) comes to 58
			If checksum is Ok	If the program slot indicated in info block
			sends byte 6, else	above is full then byte 33 is sent in reply.
			byte 43 is sent		If user wants to overwrite prog. then send
						byte 6 else send 21 to abort.
Assuming no checksum				i.e. (256*a)+b bytes. Checksum is calculated on
error the program is				this data and if Ok byte 6 is sent, else byte
sent						43 is sent.
