Things have more or less stabilised....I'll be working with the p87c52 since there are a lot of pieces available with my guide....also i'll use the a276308a eprom with it and a 74hct573 latch..
I'm going to get the pcb done today.....

Andy i wanted to know if the coding i write should in anyway be altered since the program is stored in external eprom...or is it enough just to ground the EA pin..
This is the simple code i have written to toggle output every 5 ms...Also i want to confirm is PORT 0 and PORT 2 can be used or are they sacrificed because the carry address/data..
thank you,


/*toggle output every 5ms */
#include <at89x51.h>
main()
{
TMOD = 0x01; /* TIMER0 at Mode 1 */
while (1)
{
TH0 = (65536 - 4608) / 256; /* 5ms */
TL0 = (65536- 4608) % 256;
TR0 = 1; /* start timer */
P1=0xFF
while (!TF0) /* wait for overflow */
{
}
TR0 = 0; /* stop timer */
TF0 = 0; /* clear timer overlow flag */
TH0 = (65536 - 4608) / 256; /* 5ms */
TL0 = (65536- 4608) % 256;
TR0 = 1; /* start timer */
P1=0x00
while (!TF0) /* wait for overflow */
{
}
TR0 = 0; /* stop timer */
TF0 = 0; /* clear timer overlow flag */
}
}


-rahul