hi,
the compiler might "suddenly" stop using DJNZ; eg, if all the available registers get used up for other things

Andy, if there is not enough registers for DJNZ then compiler uses memory locations because DJNZ may be used both with registers and direct memory. For example, next code:

	volatile unsigned char x;
	unsigned char a=0;

	for (x=200; x > 0; x--)
		a++;

is compiled into:

       CLR      A
       MOV      R7,A
       MOV      0x08,#0xC8
FOR_CYCLE:
       INC      R7
       DJNZ     0x08,FOR_CYCLE

Regards,
Oleg