I have MSC1211EVM board and a pcb with AM29F016D, DS1307, 74HC573 etc.
- I used ribbon cables of 10inches lenght approx. to connect pcb to EVM.
- Port0 is connected to flashmemory databus, and Port2 is used for control signals as given below:

#define MEM_OE P2_0
#define MEM_WE P2_1
#define MEM_RY_BY P2_2
#define MEM_RESET P2_3
#define MEM_CE P2_4
#define LATCH1 P2_5
#define LATCH2 P2_6
#define LATCH3 P2_7
#define MDATA P0

#define SCL P1_7
#define SDA P1_6

- pcb is powered with 5V tapping from EVM board.
- I wrote a small program as given below to test board:

#include<8052.h>
void main(void)
{
P0 = 0xAA;
}
compiled with SDCC compiler and loaded to EVM.
- measured voltages at P0(it has 10K pullups connected) and expected either 5V or 0V, but voltages are very random ie 3.2V, 1.8V 2.5V etc.
- Now I just added two line of code to the above program as given below
#include<8052.h>
void main(void)
{
P3_6 = 0;
P3_7 = 0;
P0 = 0xAA;
}
and now voltages are perfectly all right as i expected (either at 5V or 0V)

- why my EVM is behaving like this ?
- whether 10inch cable is creating problem i.e loading MSC1211 controller.
- do I need to provide a buffer between EVM ports and pcb(with AM29f016D and DS1307).
- Is it ok if I powered pcb from EVMboard


Kindly reply asap
P.Ravi