LVP

[Bilal]

Often a question arises in my mind. Why PIC offers two type of Programming on a same Chip.

a) Standard programming with Vpp 12v.
b) and Low Voltage Programming.

And if a Chip has LVP which req only 5volt level and 3 PINs
then why we have to make Vpp 12v??
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[temtronic]

One reason is for 'legacy' purposes, so old guys like me with 'old style' programmers can still carryon....

also, but more importantly..

If set to LVP, that pin cannot be used for general purpose I/O ! Not a big deal on a 40 pinner....but on a 8 pinner(12F683) that can be BIG trouble !!
Details are in the datasheet ,look for ICSP chapter....

[bkamen]

Part of LVP comes from the ability for the chip to self program.

Once they added that, it would have been easy to make it available from outside. So they did.

now, with one feature (being able to have bootloaders), they can also now put PIC's in a system where another controller can reprogram this controller.

Pretty much like an FPGA. I've worked on FPGA projects where the FPGA is going timing critical work for a 400MHz Intel Xscale CPU. The "firmware" for the FPGA was sent at bootup by the Intel CPU and was kept on disk.

You could now do the same with PICs.

Pretty cool.

-Ben
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Dazed and confused? I don't think so. Just "plain lost" will do. :D

[Ttelmah]

Pins, and security.
It is very rare to have enough pins on a PIC. LVP, costs too many pins, even on a 64pin device!....
Also, there are things that you can do with high voltage programming, that you can't with LVP. If you are securing the device, you have to perform a high voltage erase, before you can program it again. Most commercial users _will_ be securing the chips.
You no longer actually have to generate Vpp. On the early chips, you supplied the programming current (often quite a few mA needed). On modern chips you only have to provide a 'reference' voltage, at the higher voltage, and the chip then generates the internal Vpp to match this. Generating the required voltage a few uA, is easy with a charge pump.

Best Wishes

[bkamen]

[temtronic]

'they' added it , cause they're 'engineers' ? and convinced marketing it'd be a great thing !

Probably the same guys that gave Ford the 'flaming F150' master cylinder pressure switch !!