My oldest i8751, dated 1979, is a 12 MHz part. You've referred to these 8 MHz parts before. What are they? My very earliest i8748 was an 11 MHz part, and that was from 1978. The datasheets don't reflect slow parts like that. Where do you see an 8 MHz-max part?

If you write to a port, it takes 1 cycle to do the write. If it's an external port, it takes one cycle to do the write. if the bus cycle is 12 clocks, and the system clock is at 24 MHz, that's a half microsecond. If it's a two-cycle instruction, which an external port write would be, it will take a microsecond, right? The i8255 will have managed the hardware handshake for you by then. How long will it take for the IIC device to get that done? Will it be timely, i.e. if the device tells you it's ready to transfer a byte, will the transfer happen within, say, 4 microseconds? No? Just how will that work?

RE