What is the Best Practice to Leave Unused Pins in a Micro-controller

what is the best practice to leave unused pins in a micro-controller

http://www.edaboard.com/thread337418.html[6/4/2015 4:03:50 PM]

Forum Digital Design and Programming Microcontrollers



Part & Inventory Search

Welcome to EDABoard.com

Threads Without Replies

Sponsor

[ Unanswered Posts ]

lpc2148 timer pgm is not working hi frnds....... here i am posting my code to generate 1s delay using timer 0 in lpc2148. link to learn 8051 Fosc=12Mhz CCLK=60Mhz PCLK=60Mhz but this code is not generating desired delay...Posted By rajslr. Today 08:56 in Microcontrollers

rxSetupTime and RX/TX switching time Hi, Could someone please explain rxSetupTime, RX/TX switching time and RX-TX turnaround time? According to paper [1], The rxSetupTime is the time to switch the radio from IDLE to SLEEP and...Posted By vreg. Today 08:45 in RF, Microwave, Antennas and Optics

research work in microstrip antenna with optical communication Hi all Can you give me details about research work going on microstrip antenna with optical communication any Ph.D. thesis or IEEE paper regards, KartikPosted By kartikkhurana. Today 08:32 in RF, Microwave, Antennas and Optics

How Generate Signal with frequency and duty Cycle?(8051 Assembly) Hi, suppose we have frequency and duty cycle in R7 and R6 now how generate signal with internal interrupt? Thanks a lotPosted By panda1234. Today 08:31 in Microcontrollers

design layout in TANNER Can anyone help me to design the layout in TANNER EDA tool L-edit..If there is any link for this procedure??Posted By Ponmalar21. Today 08:06 in ASIC Design Methodologies and Tools (Digital)

Remember Me?

Resend activation?Lost password?Register

Activity Stream Search Help Rules Groups Albums Blogs

What's New?New Posts Unanswered Posts FAQ Forum Actions Community Quick Links Advanced Search

+ Post New Thread Results 1 to 16 of 16

LinkBack Thread Tools Search Thread

12th May 2015, 08:20


Hi,

I am using the 8F4620 mcu, in my project some of the pins in the device are left un used, some pins on the PortB, some on the PortA.

What is the best practice to leave these pins without causing damage to the mcu. Normally I leave them un connected (just open), is it necessary to connect these to pullup resistances or LEDs (through resistances) ??

thanks a

#1

Join Date:Posts:Helped:Points:Level:

Apr 20121337 / 71,1187

arbj2

Full Member level 2

Forum



New Replies

EE News, Tips and Resources

Recently Updated Groups

Allegro PCB Editor 16.6 (1)is there any library for image processing codes in vhdl like imresize or imshow ?? (3)gsm modem restarted while OUTPUT will turn ON/OFF. (4)RC-extractions/coners -> how many should be done for SignOff (6)Will an AC electromagnet respond to harmonics? (8)lcd interfacing in spartan 3E using vhdl (19)Array Antenna Simulation and measured differnce (8)Errors of inout ports & their associated expressions. (2)[moved] D-Type Positive-Edge -Triggered Flip-Flop with discrete components? (5)Radiation pattern in CST studio (2)How do I use Float in xc8 compilor ? (4)Triac flashing with no gate signal (1)[moved] Why I can't reply post? (1)Assembly Code for data saving from keypad in Registers(8051) (9)delay calculation in vhdl (2)How to read ram in test bench? (1)How to multiplex serial data and send it to the PC? (1)Universal SMPS design (1)not equal phase feeding of patch array elements, what would be S11? (3)Password problem on windows 8 (6)Logic Formal Verification -> how does it work? (10)Signals and variables in VHDL (25)Is it possible to make Capacitive touch operated tone generator with microcontroller? (1)LVPECL to LVDS termination. (4)linear variable resistor but output voltage is not linear (7)

Synchronous SRAM Family sports On-Chip Error-Correcting Cod 5/28/2015 Nucleus RTOS aims to wear IoT well 5/19/2015 Digital signal controllers address power supply challenges 5/18/2015

VLSI Jobs - World Wide, India VLSI Group, VLSI,

Reply With Quote

12th May 2015, 08:21

Re: what is the best practice to leave unused pins in a micro-controller

Configure them as digital input pins and connect them to GND.

#2


Apr 20132,415499 / 49911,77126

milan.rajik

Advanced Member level 5

Reply With Quote

12th May 2015, 09:28


but what if I leave them not connected to anything, will this damage the mcu ??

#3


Apr 20121337 / 71,1187

arbj2

Full Member level 2

Reply With Quote

12th May 2015, 09:28

12th May 2015, 09:49 #4



Sponsor

Top Helped / Month

Top Posters

Top Experience Points

Semiconductor Jobs,India, Free EDA Tools, VLSI programming group, Project help, Microwave engineering, Metamaterials, RF circuits and systems design

FvM (11), Warpspeed (9), BradtheRad (6), milan.rajik (5), betwixt (5)

FvM (31090), alexan_e (11475), keith1200rs (10885), bigdogguru (8846), IanP (7943)

FvM (186799), IanP (160151), bigdogguru (59569), tpetar (54409), tsb_nph (53644)


No, it will not damage the MCU but make then as digital input pins.


Apr 20132,415499 / 49911,77126

milan.rajik


Reply With Quote

12th May 2015, 09:49

12th May 2015, 10:25


#5


Apr 20101,249253 / 2538,50222

srizbf


Originally Posted by arbj2

but what if I leave them not connected to anything, will



open pins can easily pickup noise. sometimes difficult to debug. so connect either to 1 or 0 level.

this damage the mcu ??

Reply With Quote

12th May 2015, 11:01


Could this damage the chip ??

#6


Apr 20121337 / 71,1187

arbj2

Full Member level 2

open pins can easily pickup noise.

Reply With Quote

12th May 2015, 11:04

Re: what is the best practice to leave unused pins in a micro-

#7

Join Date: Feb 2007

malli_1729

Full Member level 3

Achievements:



controller

You can't leave CMOS pins OPEN.That can damage the IC itself... IF they are inputs Pull Up/Down

Location:Posts:Helped:Points:Level:

INDIA16025 / 252,50511

Reply With Quote

12th May 2015, 11:04

12th May 2015, 12:06


so if I configure the unused pins as digital inputs, then do I have to connect pullup resistances to them ?? or should I just configure as input and leave it.

Alternatively Is it OK to configure as output and keep them low through firmware

#8


Apr 20121337 / 71,1187

arbj2

Full Member level 2

Reply With Quote



12th May 2015, 12:13


You can leave them in any configuration. It always protected by internal diodes. But good practice to leave them as digital input. Also, pull-up if available. But not mandatory.

1 members found this post helpful.

#9

Join Date:Location:Posts:Helped:Points:Level:

Oct 2011Tallinn, Estonia525120 / 1203,13613

Easyrider83


Love me or hate me. All infractions will be ignored.

Reply With Quote

12th May 2015, 12:22


If I have the space, I'll run them to a non-populated connector and set them as outputs set to low.

#10


Oct 201217750 / 501,3648

spudboy488

Full Member level 3

Reply With Quote



12th May 2015, 12:23


Not properly damage, but could increase power consumption in the presence of a noisy environment if these inputs are type of CMOS, but as far as I know most microcontrollers have general inputs of type ST.

#11

Join Date:Location:Posts:Helped:Points:Level:Blog Entries:

Nov 2006Rio de Janeiro, Brazil4,096474 / 47413,546275

andre_teprom

Super Moderator

Originally Posted by arbj2

Could this damage the chip ??

-------------------------------------------------------------------------------------------------- Part of the world that you live in, You are the part that you're giving ( Renaissance )

Reply With Quote



12th May 2015, 12:52


The input buffer of digital inputs will sink additional power if inputs float to an intermediate level. So in a low power design, you'll never leave digital inputs floating. Configuring the unconnected pins as analog input (if available for the respective pins) would avoid this issue.

That's my preferred option for unconnected pins that have no pull-up or pull-down

#12

Join Date:Location:Posts:Helped:Points:Level:

Jan 2008Bochum, Germany31,1049688 / 9688186,850100

FvM

Super Moderator

Awards:

Alternatively Is it OK to configure as output and keep them low through firmware



resistors.

Reply With Quote

12th May 2015, 17:04


If you want to left it as open Better to configure as an output compared to configuring as an input. Unless until you are not going to connect anything on that pin you don't even have to worry about drive strength or source current of it.

#13


Mar 201517827 / 276595

hobbyckts

Full Member level 3

Reply With Quote

26th May 2015, 10:02


thanks everyone for the tips...

I was curious as one of the pins (Txd) in a 18F4620-SPDIP mcu got damaged after working for some time. The

#14


Apr 20121337 / 71,1187

arbj2

Full Member level 2



Txd pin was connected to a SN75LBC184 RS485 transceiver. The RS485 line was long at least 10m, and the system was installed in an industrial environment (lots of heavy duty motors around), moreover there was a stepper motor near the mcu.

Do you think the unused pins could have damaged the Txd pin of the mcu ?? Curiously only the Txd pin was damaged, while other pins where all working...

Just for your information, the mcu alongwith the PCB was sealed in an aluminium box using Araldite...(the entire mcu with PCB was immersed in araldite).

Could this also be responsible for the damage ?? I know some passive components are sealed in this way, but is this method advisable for micro-controllers ???

The current consumption of



the mcu was less than 30mA, so I don't think heat could have damaged the pin...

Interestingly a similar unit (having another 18F4620 mcu, and sealed in similar manner) was connected to the defective unit via RS 485 cable, and also shared same power supply unit did not get damaged, and continues to work without any problem...

Just wanted to know your opinion...

thanks a

Last edited by arbj2; 26th May 2015 at 10:07.

Reply With Quote

26th May 2015, 17:22


Is araldite is touching any of the components in the PCB?

#15


Mar 201517827 / 276595

hobbyckts

Full Member level 3

Reply With Quote



-- Edaboard Classic

[PIC] Is this SPI Multi-Master Communication working properly ? [Doubt] | seperately excited dc motor control

Contact Us Forum for Electronics Privacy Statement Terms of Service Top

All times are GMT +1. The time now is 10:38.

Powered by vBulletinCopyright 2010 vBulletin Solutions, Inc. All rights reserved.

SEO by vBSEO 2011, Crawlability, Inc.

Today, 04:12


yes almost all the components, the components are immersed in Araldite..

#16


Apr 20121337 / 71,1187

arbj2

Full Member level 2

Reply With Quote

Please login+ Post New Thread

I2C Sniffer using GPIO pins of ATtiny85 Micro-controller? (5)How to select the micro-controller based on the I/O pins? (10)SOC Encounter and unused pins (0)What to do with 74HC245 unused pins? (1)IC question (unused pins) (7)

Similar Threads

edaboard.comwhat is the best practice to leave unused pins in a micro-controller

5jb20vdGhyZWFkMzM3NDE4Lmh0bWwA: form3: vb_login_username: User Namevb_login_password_hint: Passwordinput7: cookieuser: 0

5jb20vdGhyZWFkMzM3NDE4Lmh0bWwA: form1: query: submit: styleid: 6

Documents

What is the Best Practice to Leave Unused Pins in a Micro-controller