Hi there,

I wrote some code in asm to interface a 8031 controller to a 93C46N serial E²PROM. The connections are S to P1.7; C to P1.6; D to P1.5 and Q to P1.4 (I also tried with ports P3.0 to P3.3) with the same strange result when I try to read from the E²PROM.

The datasheet said that the Q-line goes from Hi-Z to low on the last clock 0-1 transition. Well, when I check on the scope it goes on the last but one clock 0-1 transition.
Question is: "What is the last"? Since I use 8 bit organisation, I need 10 clock 0-1 transitions: 1 for startbit, 2 for OP Code and 7 for address. So I expect Q line on a low level after 10 clocks but on the scope I see it after only 9 clocks.

I found something confusing in the datasheet from ST about the read cycle. They wrote "a dummy '0'bit is output first followed by the 8 bit byte ....." but when you look at the timings for a read, you see that the first bit send the Q15/Q7 bit is, not a dummy '0'. How many clocks do you need to get 8 bits out of the E²PROM? When you look at the timing I should say 8, when you read the text I should say 9 ??!??

The data I got from any address is always 250 or 251 even if I programm something else in a specific address. But the problem is "What is wrong, the reading or the writing ;-)"

So:
Can anyone help me out here??
Does anyone have some asm code for microwire interface??

Thanks in advance
Alain