Thanks. It seems that the Philips chip is using a similar mechanism, but you are right- it is not the same.

However, your code:

GoToBoot:
mov AUXR1,#020h ;enable boot
mov r0,#20 ;oscillator freq = 20Mhz
mov r1,#6h ;program status byte
mov dptr,#0 ;specify status byte
mov a,#0ffh ;nonzero required
call 0fff0h
jmp $ ;wait for watchdog to reset

Is doing almost the same as mine:

EA=0;
FCON=0x00; /* Probably should be 0xF0 */
AUXR1 |= ENBOOT; /* Enable boot flash area */
_opc(0x02); /* LJMP 0xF800 */
_opc(0xF8);
_opc(0x00);

But the vector for the bootloader is 0xF800 and there are different parameters.

I must be missing something very simple, as I am convinced I am doing what the datasheet suggests and the same as ATMELs sample code. Perhaps there is a fault on my chip or in my circuit. I will keep trying, but thank you all for your help.

Andy