Could anyone please post some info on timer chips? I'm looking for timers controlled by PC serial port. Need three timers on a common crystal osc base that are low jitter. Only 0 to 200 Hz pulse train and a lot of control resolution over that range, like 16bit. And also some provision to initially sync the three timers as in an absolute hardware sync, not software, and then the ability to adjust the timing of each. Do I have to roll (learn to program) my own?
It appears what you are asking could be accomplished by a Microchip PIC device. Go to Microchip's web site and look up the specs for the 16F628 chip. It has three internal timers that can be slaved to an external oscillator. Two of the timers TMR0 and TMR2 although they are eight bit timers can be quite versatile because they have pre and post scalers. In effect they can count to 16 bits. TMR2 is a 16 bit timer. They can generate interrupts and TMR2 can interrupt at a loadable value, PR2. And the 16F628 is dirt cheap. Costs less than a couple of LEDs. There may be other PIC chips that could be better suited for your purposes, I'm only familiar with the 628. Oh, the 628 has a built in USART capability which can communicate with a PC via a serial port.
I'm working on a 16F628 electronic ignition project where I use TMR0 to count the time between revolution pulses and TMR2 to count down the necessary spark delay time. The beauty of using these timers is that once loaded and started that keep on counting regardless of what the rest of the software is doing. They just keep on ticking.
Of course to utilize all these features you have to roll your own code and then download it onto the PIC.
"Marlowe" wrote in news:w2%id.19200$ snipped-for-privacy@newsread1.news.pas.earthlink.net:
Yes, I believe hardware timers is the only way to provide steady pulse trains regardless of all other code execution. I'm looking for the minimum needed to provide three variable pulse trains controlled by the PC serial port. What about using a Basic stamp (easier for me) for the serial stuff and separate chip with 3 timers? What timer chips should I be considering? Someone had used an 82C54 with a stamp. I've been fooling around with CMOS 4000, so what do I know. They do function well for low freq stuff, but changing divider outputs on a breadboard is getting tiring and I can't keep track of what changes are made verses time. It's like the stone age here.
The BASIC STAMP is certainly a possibility, but out of my area of expertise. It does have a PIC embedded in it so you might to look into the PIC on the STAMP to evaluate the number and capability of the internal timers. If it is using something like the PIC 16F628 or the 16F648 you can possibly do everything (serial IF, timers, etc) within the STAMP. The other possibility is to use the PICAXE system. Do an internet search on this keyword. The last time I looked on Ebay they had several for sale.
"Marlowe" wrote in news:yhEjd.8567$ snipped-for-privacy@newsread3.news.pas.earthlink.net:
Just realized that MBASIC was available for the 16F628. I wanted to avoid ASM if possible.
PICAXE looks like a good cheaper alternative to the STAMP (despite falling dollar). I like the built-in bootstrap and no need for programmer board. Thanks for the info.
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