Electronics > Microcontrollers

Confusion about PIC18F4450 PIC18F2550 pin, ICSP

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I wonder if the pin 12 (NC/ICPGC) and 13 (NC/ICPGD) pic PIC18F4450 TQFP (44-Pins) (although this carry the same on pins 15 and 16) are equivalent and do exactly the same as the Pic PIC18F2550 DIP (28Pins) Pin 27 (RB6/PGC) and 28 (RB7/PGD), when programmed via ICSP. Apto.25 311 Pag-9. the datasheet.

PIC18F4450                      PIC18F2550  
  P.12 (NC / ICPGC)     =        P.28 (RB7/PGD)  
  P.13 (NC / ICPGD)     =        P.27 (RB6/PGC)


They do the same thing, the difference is that on the 4450 you dont lose IO, as those pins are reserved for ICSP


You mean I can get more pins RB6 assigned (PGM) and RB7 (PGC) of PIC18F445 pic.
Since these pins apart PIC18F4550 is free to ICSP programming instead of using the RB exclusively ..


Jon Chandler:
The data sheet is the best reference on this.  The pin out diagram has a footnote for 44 pin devices, referring to section 25.9, which says:

--- Quote ---
25.9 Special ICPORT Features (44-Pin TQFP Package Only)

Under specific circumstances, the No Connect (NC) pins of devices in 44-pin TQFP packages can provide additional functionality. These features are controlled by device Configuration bits and are available only in this package type and pin count.


The 44-pin TQFP devices can use NC pins to provide an alternate port for In-Circuit Debugging (ICD) and In-Circuit Serial Programming (ICSP). These pins are collectively known as the dedicated ICSP/ICD port, since they are not shared with any other function of the device.

When implemented, the dedicated port activates three NC pins to provide an alternate device Reset, data and clock ports. None of these ports overlap with standard I/O pins, making the I/O pins available to the user’s application.

The dedicated ICSP/ICD port is enabled by setting the ICPRT Configuration bit. The port functions the same way as the legacy ICSP/ICD port on RB6/RB7. Table 25-5 identifies the functionally equivalent pins for ICSP and ICD purposes.

Even when the dedicated port is enabled, the ICSP functions remain available through the legacy port. When VIHH is seen on the MCLR/VPP/RE3 pin, the state of the ICRST/ICVPP pin is ignored.

Note 1:
The ICPRT Configuration bit can only be programmed through the default ICSP port (MCLR/RB6/RB7).


--- End quote ---

So yes, you can use the alternative pins for ICSP provided you set the proper configuration bit via the normal ICSP pins.

I'm angry because ... Imagine that we have a PCB that will track special ports 12 (ICPGC) and 13 (ICPGD) instead of 16 (RB6/PGC) and 17 (RB7/PGD) tracks are already made to schedule these pins. For if before using special pins I have to program them first by RB6 and RB7 and then activate the Fuse "ICPRT", would have to put in the PCB jumpers for programs after the first PIC and disable jumpers for programming by the second special port. Instead of saving those tracks would have to put four tracks instead of two.
Am I wrong or not? ...
Thank you.


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