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Simultaneous PIC reset

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Krumlink

New Member
What ways could I simultaneous reset 2 PIC's? I am working on a PIC to PIC communication, and I want to know how I could reset them at the same time.
 

Papabravo

Well-Known Member
I may be missing something but the obvious answer is to connect MCLR* on both processors to the same reset circuit.

The next most obvious way is to design things so it doesn't matter which order they get RESET in.
 

Krumlink

New Member
They will be communicating through the PSP on the 18F4620.
 

Sceadwian

Banned
That does seem like an unusually easy question for you to be asking Krum.. You just tie the reset lines together, if you still need to reset them separately use an OR gate from their original reset circuit.
 

Sceadwian

Banned
What is PSP? I see it listed as an interface for pics but I'm not familiar with it.
 
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Krumlink

New Member
That does seem like an unusually easy question for you to be asking Krum.. You just tie the reset lines together, if you still need to reset them separately use an OR gate from their original reset circuit.
I was just going to use a DPDT push button and send each side of the MCLR reset through each side. I wasn't sure if it would cause problems during programming, thats why I asked before I build the circuit.
 

Krumlink

New Member
Off Topic:
Do you have a vacuum desoldering pump? I had one that came in a radioshark tool kit (aunt got it for me) and I was desolering and it got plugged and shot the cap and spring out! I lost the spring, and has this ever happened to you?
 

Sceadwian

Banned
Krum do NOT use a DPDT switch, there is no garuntee of any kind that both side of the DPDT switch will close at exactly the same time. Use an SPST and tie the reset lines together. Having the two reset lines shouldn't hurt anything during programming as long as you only try to program one at a time. Also make sure you use a RC filter to debounce the switch in hardware, contact bounce may cause them to not start up at exactly the same period of time.
 
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Krumlink

New Member
The reset does NOT work when both MCLR's are together, and I wanted them to boot at the same time, but oh well.
 
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Sceadwian

Banned
Why doesn't the MCLR work when they're tied together?
 

Krumlink

New Member
Why doesn't the MCLR work when they're tied together?
During programming, it gives a device address error. I am just going to have independent reset switches, since I already put them on. Also, there is no benefit of having them reset at the same time since they are doing independent tasks, and only talking when one needs to send data to the other pic.

I may yet redesign the purpose for PIC to PIC communication through SPI.
 

Nigel Goodwin

Super Moderator
Most Helpful Member
Regardless of how you communicate between them, there's no reason (or purpose) in trying to make then reset exactly together.

How much data are you trying to transfer, and for what purpose?.
 

Krumlink

New Member
Regardless of how you communicate between them, there's no reason (or purpose) in trying to make then reset exactly together.

How much data are you trying to transfer, and for what purpose?.
Low amount of data, one is the master and the other is the slave. the slave will handle the LCD, 8 LED indicators, various LED's and etc. It basically sends and receives data from the master, such as what LED's to light up, and LCD display. Simple data transfers.
 

blueroomelectronics

Well-Known Member
The I2C or SPI bus are ideal for this sort of thing. The PSP port can be reassigned to the LCD display.

That said, careful and smart use of your I/O can sometimes get everything you want from a single PIC. Or use a larger PIC.
 
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Krumlink

New Member
going back to the I2C, the only connections I need are SDA and SCL right? So on the 4620, that would be pin RC4 and RC5 correct?
 
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