having problems to read a PIC16F877

[vanessa]

hi everyone, i am trying to read a PIC16F877 that is on a general control board which controls an engine. there is also a lattice fpga on this board. the thing is that i am trying to read the program that is on the pic device to modify a few things. but the VDD pin on the connector has been cut, is there any kind of modification that i can do to the circuit to be able to read the pic device? i am using mplab icd 2. the board was given to me like that to recover that code, but because pin 2 is missing, the mplab icd 2 reads a lack of power from the pic device. i have attached the schematic of the programming connector (VCC=24V it powers the entire board, and CR1 is a ceramic resonator) thanks everyone!

[mister_e]

Can't an ICD 2 be set to not supply the target board?

[Acetronics2]

Hi,

From ICD2 Manual note on P 11 : Pin 2 of the ICD2 MUST see a voltage ...

so, you must choose the " POwer supplied to the target option" of your ICD2 ( in MPLAB )

Now, I suppose your board supplies 5 v to the PIC ... The ICD2 will supply 5 volts to the target ...

No danger to fry PGC or PGD pins ....

Alain

[vanessa]

i have set the mplab to not supply power to the target, and it still it doesn't recognize it. i was told that it could be because, whether i choose for the mplab to power the target or not, is through pin 2 that the mplab recognizes the target as being powered. so, because that pin is missing, even though the target is properly powered, the mplab keeps sending errors ( when i connect the mplab to the target, and the target is powered by an external source this is what appears on the screen:

Connecting to MPLAB ICD 2
...Connected
Setting Vdd source to target
ICDWarn0020: Invalid target device id (expected=0x4D, read=0x0)
...Reading ICD Product ID
Running ICD Self Test
... Failed Self Test. See ICD2 Settings (status tab) for details.
MPLAB ICD 2 Ready

)

[vanessa]

i forgot, when i use the configuration i mentioned before (connecting mplab to the board via usb and powering the target with an external source). these are the power settings i get:

target vdd: 0.00
target vpp: 12.46
mplab icd 2 vpp: 12.46