| ??? 02/05/07 20:01 Modified: 02/05/07 20:19 Read: times |
#132084 - What do you mean \"ummm\" Responding to: ???'s previous message |
Mike Stegmaier said:
First of all, what role does the 18.432 MHz oscillator or crystal have in your system? You can't use a crystal of that frequency in a crystal oscillator configuration on the HMOS MCU, Its CMOS. My chip is an intel 80C51-BH. It has worked with it before. I've got the databook for that part in my lap right now, and it is not specified for operation above 12 MHz. Are you willing to invest all this time, effort, and expense, in something that, at best, MIGHT work properly? and, in order to get to a suitable baud rate for standard asynchronous communication, you'll have to use T2
I don't have T2. My is an 8051 compatible chip. It doesn't have the 8052 features. Gee, Intel thinks you do. Their databook says it has two 16-bit timers. just to generate common baud rates with that speed even if your part does work at that rate, which it shouldn't.
My previous system allowed me to work at a 19.2kbps baud rate with that crystal. and the same chips were used then. However, if you choose to use CMOS address latch... Actually, I'm going to leave my latch alone and go with 74HC573. You DO know that that's a CMOS device that requires pullups, right? The only pin that might be affected by CMOS gates is the PSEN pin, the clock, and the parallel port data.
The logic works, but I have to work with what I have available to me. How can you know that? Have you examined it with oscilloscope and logic analyzer? Do you even know what a logic analyzer is? It's not a "logic probe" which has a one-shot and an LED. It's a sophisticated instrument with many, in some cases hundreds, of channels, which it samples, stores, and displays. Imagine a 250-channel oscilloscope ... one that only displays logic levels. OK, so you're using the CMOS part, which IS static. That's good. You can do whatever you want with the oscillator input. How does that help your part operate at 1.5x its' specified rate? Are you playing "fast and loose" with the spec's? RE |
