help with EA bar pin of p89v51rd2

[digantshah]

hi everyone,
i have a confusion that if i keep the EA bar pin high will it block the on chip 64k flash or it is for external memory connected seperately

 

[colin mac]

If /EA is high, it will execute from internal memory.

 

[Papabravo]

EA* is only for program memory. When it is driven low, all instuction fetches are from external memory using P2/P0 for the addrees/data bus and using PSEN* (Program Store Enable *) as the OE* for the external memory.

Data memory is altogether different. That uses ALE, RD*, WR*, and P2/P0. Data memory access only happens with MOVX instructions. No other instruction can generate RD* or WR*

Read the datasheets very carefully to avoid going astray.

 

[digantshah]

thank you papabravo

so if i have understood it
the 64k on-chip flash of p89v51rd2 is the data memory and the EA bar pin has no effect on it

please correct if wrong

 

[Papabravo]

That is just backwards. The 64K of on chip flash is in all likelihood the PROGRAM memory. If EA* is high your program memory fetches will come from the internal flash. If EA* is low then the program memory fetches will come from what ever memory is there. This is actually a useful diagnostic tool.

1. Take EA* low
2. Take Reset High then Low
3. Force a NOP instruction on P0 during PSEN* == 0
4. Wathe the Address bus count from 0 to 0xFFFF and repeat

 

[digantshah]

store program in the on chip flash

when i flash my p89v51rd2 does the program directly go to the on chip flash?

how to store program on the on chip 64k flash program memory

need help.... very urgent...