Vpp Generation Failed
John Couture
Posts: 370
PROBLEM:
I'm getting a "Vpp Generation Failed" error message when I try to download program to SX18 to perfboard.
TEST PROCEDURE:
1) Downloaded a program to SX18 while it is in my solderless breadboard (beeps a piezo and displays a message on an LCD)
2) Program ran ok while SX18 in solderless breadboard.
3) Took the same SX18 chip and inserted it into my prototype perfboard.
4)·Program ran OKl (beeps a piezo and displays a message on an LCD)
5) However when I try to reporgram the SX18 in the perfboard using the same computer and program, I get the error.
MY CONCLUSIONS:
1) perfboard is at least wired ok for power and the LCD
2) is it possible that the SX-Key (and therefore the resonator) is too far from the chip?
3) perfboard has on-board regulated power (LM387A, diode, two 100uF caps)
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John J. Couture
San Diego Miramar College
I'm getting a "Vpp Generation Failed" error message when I try to download program to SX18 to perfboard.
TEST PROCEDURE:
1) Downloaded a program to SX18 while it is in my solderless breadboard (beeps a piezo and displays a message on an LCD)
2) Program ran ok while SX18 in solderless breadboard.
3) Took the same SX18 chip and inserted it into my prototype perfboard.
4)·Program ran OKl (beeps a piezo and displays a message on an LCD)
5) However when I try to reporgram the SX18 in the perfboard using the same computer and program, I get the error.
MY CONCLUSIONS:
1) perfboard is at least wired ok for power and the LCD
2) is it possible that the SX-Key (and therefore the resonator) is too far from the chip?
3) perfboard has on-board regulated power (LM387A, diode, two 100uF caps)
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John J. Couture
San Diego Miramar College
Comments
for programming an SX, the SX-Key generates a programming voltage (Vpp) of approx. 12V and applies it to the OSC1 pin of the SX to be programmed. External loads on the OSC1 pin can cause Vpp to break down, and the SX-Key IDE will report an error (Vpp generation failed).
Usually, resonators, or crystals connected to the OSC1 and OSC2 pins can stand these 12 Volts, and don't cause an excessive load to Vpp, so they need not to be removed or isolated from OSC1 while programming the SX (but they must for debugging). External clock sources, like a clock generator, or a PLL clock connected to the OSC1 pin - on the other hand - may cause too much load for Vpp, even when the clock generator's output is switched off (some PMM clock devices allow for that).
What type of clock are you using on the perfboard? If it is a clock generator, you should provide a jumper between its output and the OSC1 pin and pull it while programming.
I don't think that the distance between the SX-Key and the chip cause this problem because while programming, frequencies on the OSC1 and OSC2 lines are relatively low.
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Greetings from Germany,
G
Thank you! You saved me a lot of work! Your description helped me understand what was going on and I found the problem!
Well here is another one you can add to your diagnostic knowledge (laughing at myself). If you reverse the OSC1 and OSC2 leads, you get a Vpp error. Some days are just harder than others! I though I had checked and rechecked those lines. Must be gremlins in the middle of the night that came and switched them!
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John J. Couture
San Diego Miramar College
good info - I think I'll add this to the next edition of the SX FAQ. Also good to know that Vpp connected to the OSC2 pin does not kill the SX
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Greetings from Germany,
G