The rep (for Atmel-WM) says that I can set this with software and jump from internal code to external code. Has anyone had any luck with this??
I am using the Temic 89C52RD2 and I need to start up in internal flash. But I want to be able to jump to external code later. A Temic rep told me that if I set !EA low in software (by pulling it low with another line P1.4 in this case) I would be able to accomplish this. The EE who designed the board pulled !EA high through a resistor and then tied P1.4 to !EA. I have set P1.4 low in code but I don't get any PSEN's. Ideas??
Did you set lock bit 1 when you program the parts? Lock bit 1 forces the chip to look at EA only at reset.
I trying to say that is a mistake to set lock bit 1.
Will clearing LB1 allow the processor to be effected by !EA
I never tried this personally. All I know is that the manual does say "If security level 1 is programmed /EA will be internally latched on reset.".
How do you change this register? The white paper doesn't say...no address anyway. Do I need to use a programmer of some kind?
Here is my (non expert) take on reading the Rev F data sheet. Since the default value is level 4, you need to use a parallel programer to erase the chip the reload the boot loader (available from ATMEL). This should put you at level 0. Yuck.
I just got that same explanation from the Temic rep. Thanks, I do appreciate all the help. Stephen Kerslake