View previous topic :: View next topic |
Author |
Message |
Nora
Joined: 23 Mar 2008 Posts: 50
|
Use 3.3V to program Low voltage chips? |
Posted: Mon Jul 11, 2011 2:53 pm |
|
|
Hi-
I'm trying to make the jump from 5V to 3.3V and have had a series of bad decisions and things that don't work etc. I need to get a programmer-chip setup that is compatible with both MP Lab and the CCS compiler.
I'm currently using the PIC18F2423, and someone pointed out that the PICLF2423 is really what I need.
The LF version is not supported by MP Lab and I'm not even sure that it is a real part. Every time I try to order it from the Microchip website, my cart goes empty. It goes into the cart, but I cannot purchase.
Frustrating!!
When programming a low voltage chip, does the programming voltage need to be 3.3V? I ask because I have a PICDEM plus board that does not have a 3.3 supply.
Is it necessary to use pin B5 for ICSP, and if so, which pin is unused, B6 or B7?
What about fuses? Use something to indicate low voltage programming?
Thanks in advance for help!
Nora |
|
![](templates/subSilver/images/spacer.gif) |
PCM programmer
Joined: 06 Sep 2003 Posts: 21708
|
|
![](templates/subSilver/images/spacer.gif) |
Nora
Joined: 23 Mar 2008 Posts: 50
|
|
Posted: Mon Jul 11, 2011 5:56 pm |
|
|
Thanks!
But does the low voltage operating chip need to be programmed with low voltage? I'm confused...my USB puts out 5V, so how do I program with 3.3?
N_N |
|
![](templates/subSilver/images/spacer.gif) |
PCM programmer
Joined: 06 Sep 2003 Posts: 21708
|
|
Posted: Mon Jul 11, 2011 6:43 pm |
|
|
From your previous thread here, I see that you are using an ICD2
programmer:
http://www.ccsinfo.com/forum/viewtopic.php?t=45811
(You really should have kept this as all one thread, since it's all related topics).
The ICD2 can program PICs which are running at 3.3v. Look at the
ICD2 page:
http://www.microchip.com/stellent/idcplg?IdcService=SS_GET_PAGE&nodeId=1406&dDocName=en010046
It says:
Quote: |
Features
Supports low voltage to 2.0 volts. (2.0 to 6.0 range)
|
Quote: |
When programming a low voltage chip, does the programming voltage need to be 3.3V? |
A "low voltage" PIC can also run at +5v. The LF version simply means
that Microchip certifies that it will run over a wider voltage range than
normal 'F' PICs. So, the answer is, just go ahead and program the LF
PIC when it's running at +5v. It will program just fine. |
|
![](templates/subSilver/images/spacer.gif) |
Ttelmah
Joined: 11 Mar 2010 Posts: 19378
|
|
Posted: Tue Jul 12, 2011 2:16 am |
|
|
You program the low voltage PIC at low voltage. Some of the newer chips _do not_ support operation at 5v (look at the 18F46J50 for example - 3.6v _max_ supply voltage).
What is wrong, is not realising that the USB supply is not directly used. The ICD, has a little chopper circuit to develop it's internal supplies, and regulates these, and then has a little DAC, it uses to set the voltage fed to the actual chip.
Best Wishes |
|
![](templates/subSilver/images/spacer.gif) |
|