Issue to stop using eprom & continue using RAM in 8051 microcontroller

helderhe

Hi, I have a C51 using external eprom and RAM memory, but I want to start using the internal flash memory of the CI, but the external RAM memory.
The microcontroller I'm using is the Megawin MPC59E515A. (Datasheet: http://www.brighteamtech.com.tw/UpLoad/572/006090100010/MPC89E515A_A9.pdf )

So, I changed the pin 31 (/EA) from gnd to 5V, changed these variables:
AUXR (08Eh) <- #11b (to stop using the internal RAM memory and use the external)
XICON (0C0h) <- #00 (external interrupt control)
P4 (0E8h) <- #00 (I/O Port)

and commented the code parts that uses the eprom memory.

Then I made the following code to test the external memory

tram_loop:
mov a,#35h
mov dptr,#7ffeh ;tests the 62256 RAM memory
mov 08Eh,#03
mov 0C0h,#00
mov 085h,#00
mov 0E8h,#00
movx @dptr,a
mov a,#16h
mov dptr,#7fffh ;two bytes in the end
movx @dptr,a

mov dptr,#7ffeh
movx a,@dptr
clr c
subb a,#35h
jnz tram_loop
mov dptr,#7fffh
movx a,@dptr
clr c
subb a,#16h
jnz tram_loop

But it will never get out of the loop... not even the first jnz.
Any help, please?


Helder