How to generate reset signal form TM4C1294

Hi,

"Reset Sources" are mentioned at your Tiva MCU datasheet. You, can use the External Reset Input Pin.

- kel

Markel Robregado said:

You, can use the External Reset Input Pin. 

Are you sure?   Doesn't poster seek a Reset Output?  (i.e. "I need to provide reset signal to the chip sets on the board from TM4C1294.")

Note he seeks to "Reset" other chips on his board - and he states, "Reset FROM TM4C!"   He further notes that Reset pin of his MCU is "Input only!"

Appears poster seeks a Reset Output signal - not a Reset input source...  (as you suggest)

@cb1. Thanks for correcting me. The words got mixed up in my head.
@mamatha. Disregard my earlier post.

- kel

yes, I need a reset output signal

Regards,
Mamatha

mamatha g said:

yes, I need a reset output signal  

Thought that's what you wanted - good that.  

That said - in the "olde days" the MCU's Reset functioned "both ways."   (i.e. we simply connected that reset line to all other devices.)

In your case - wouldn't an "official" Reset generator IC prove best and safest?   Such devices detect your MCU's reset - and then (properly) output a separate (and adequate) signal to manage your other device reset requirements.   Some may even serve to correctly reset your MCU - eliminating the requirement for "normal" R-C upon MCU Reset.  

Suspect this vendor has such devices - others surely do - Digi-Key should provide quick/good search result under, "MCU Reset IC."   (one hopes)

Should you "protest" extra cost/size via this cb1 "solution" - know that it's saved you a GPIO - and that GPIO Reset will occur after your MCU has emerged from official reset - subjecting you to possible issues.   And - beyond that - GPIO may not meet rise and signal level requirements - required by your (many) other board devices.   Special MCU Reset ICs are designed by experts - they've resolved such issues - produce something "tested & which works!"  

Hello cb1_mobile,

Thanks for the input.
In the data sheet , it is given that the TM4C1294 has internal POR ckt. So external POR ckt is an optional know, which can be used during testing . Hence after processor comes up, then he has to generate reset for the on board chipsets . Is my understanding correct.

Regards,
Mamatha

Hello Mamatha

An external POR ckt has an added advantage. It can be kept at a lower threshold than the main MCU. This way if there is a device on the system that may not work reliably at the supply voltage the MCU shall also be reset to prevent a cascading effect of errors.

Regards
Amit

Amit Ashara said:

An external POR ckt has an added advantage

Hi Amit,

Thanks for your support - clearly a professionally designed/implemented "MCU Reset IC" is poster's "best bet."

While it is possible to "brew your own" - unless volumes are very high - most here would do better to "get to market fast" - and "tease out" costs downstream - as/if required.  (90%+ of the time - it is not...)

Time now for poster to search this vendor's site and/or Digi-Key - seeking MCU Reset Generator IC.

Hello cb1,

Even for high volumes, the costs do get adjusted (negotiated). Always safe to have one rather than none.

Regards
Amit

Amit Ashara said:

Always safe to have one rather than none.  

So - so true, Amit.

Thus some here (often) urge use of KISS - and simple, pre-existing, "known good" solutions.   (i.e. MCU Reset Generator IC, or API's in favor of (always delightful) direct register...)

"Shooting for the moon" too often leads to, "Failure to launch!"

mamatha g said:

In the data sheet , it is given that the TM4C1294 has internal POR ckt. So external POR ckt is an optional know, which can be used during testing . Hence after processor comes up, then he has to generate reset for the on board chipsets . Is my understanding correct.

 It is not clear what mean reset chipset, is something external to MCU or are the ON CHIP peripheral?

 If on chip then an external reset circuit can be fired by an GPIO, GPIO can also fire RESET of TIVA pulling down but it is dangerous...

 I remember old Motorola 68000 Reset/Halt lines where bidirectional, I never seen again an RST line acting as Output, clearly on 68000 lines where open collector.