Not able to ENter Programming Mode error AVR..aTMEGA128 and AVR MKII

I made an identical working PCB (with ATMEga128L) but replaced the ATMEga128L with ATmega128. THe ISP serial Programming was designed using the the same connections between MCU and AVR MKII as in previous PCB.

MKII///MCU Pins
MISO- TXD(PE1)
MOSI- RXD(PE0)
SCK- CLK(PB1)
RST- REset(nRESET)
GND- GND
Vcc- 4.9V

Unlike in my prev working PCB, the TXD RXD and CLk are always low and RSt is always High..On clicking AVR studio Programming settings..
1) target voltage is 4,9V
2) The AVRSTUDIO v6 shows fails to enter programming mode error on clicking Read device ID
3) The external resonator i am using shows 1.94 MHz freq and is connected to XTAL1 of the MCU
4)while clicking REad device ID RESET goes from hight to LOW..

I am totally confused where the real error is,,


1)The new PCb is with brand new ATMEGA128...Is the MCU now damaged...??
2) Is it something to do with bootlaoder...As i dont thing there are any bootlaoder in this new microcontroller chip??
3)Why is it not entering the Programming mode when all other settings are identical as my previous working PCB??
4) Is the failure due to switchover from ATMEGA128L to ATMEGA128??

include the setup diagram or the diagram you have used for connecting laptop, avrmkii and atmega128.

Here is the setup image of AVR MKII and ATMEGA128 ...

atmega128 atmega128l differs in the operating supply range.

128l --2.7 to 5,5
128--4.5 -5.5

diff in frequency also.
as long as you are operating in the 5v region , both are same.

if you have 3.3v supply in previous atmega128l (Vcc in figure) , then 128 will not function .

so first check it.
then id will be identified.

Thank you for your reply. Actually in my previous design the atmega128L was getting a supply of 4,9v which i did not change because the basic design remained the same. I rechecked my present design and the power suply to Microcontroller is 4.9v which i think is in valid range..morever my operating freq is 1.83 MHz so this is also not an issue..

I can see that even the AVR MKII to ATMEGA128 interface is also connected correctly so the only possible problem can be a short circuit in the PCB...Do you think the same??

if every condition is met , naturally , you have to suspect the connections.

Actually the RXD and TXD and CLk remains low all the time, but goes to high and returns to low. when read signature is clicked.
I read somewhere on forum that mosi and miso should be high all the time but go from high to low to high.

Does it mean the microcontroller is damaged if the the miso and mosi( or rxd & txd) is always low..

Hi,

my operating freq is 1.83 MHz

Click to expand...

Take care that the SPI clock frequency is low enough.
Check if lower SPI clock frequency helps..

Does it mean the microcontroller is damaged if the the miso and mosi( or rxd & txd) is always low..

Click to expand...

Avoid short circuit conditions. Use a 220 Ohms series resistor to prevent from overcurrent.

Klaus

- - - Updated - - -

Hi again,

may i ask why you use the LT oscillator? To me it seems an expensive solution.

Klaus

KlausST said:

Hi,



Take care that the SPI clock frequency is low enough.
Check if lower SPI clock frequency helps..

Avoid short circuit conditions. Use a 220 Ohms series resistor to prevent from overcurrent.

Klaus

- - - Updated - - -

Hi again,

may i ask why you use the LT oscillator? To me it seems an expensive solution.

Klaus

Click to expand...

LT oscillator is actually quite adjustable and precise for the project i need:



..It is wierd That the MKII is reading device ID if the supply vooltage to microocntrtoller is below 4v. Above 4 V it shows an error..the operating voltage for ATMEGA128 MCU is 4.5v t0 5.5v..i have no idea what to conclude from it. Please assist.

is there any possibility of 128l ic label in 128 name?

Hi,

it seems to me VCC of PCB and MKII are not conneted (at the programming header). Is this what you want?

In either way.
Check MKII VCC voltage.
Use a scope to check all programming signal levels.

Klaus