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problem with ds89c420 and isp

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ScOe

ScOe

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Hello!

I'm trying to connect ds89 to pc using schematic from maxim web. The software i use is Loader420. The problem is that when i open port and try to start loader i get following msg:

--
No response on reset from the 420
Make sure the serial cable is connected, that you are using
the right port, and have the correct voltage applied
--

the voltage is +5v regulated. I have rs232 non-inverted cable which i connect to ds232A. i get proper voltage on rst, ea and psen to enter the bootloader. Only different thing i have is 10Mhz oscillator and 22pF ceramic capacitors connected to xtal.
Could that be the problem ? I've tried with 2 different processors and on 2 different PC-s but i get same thing.
 

Loader420 is quite old, use MTK: **broken link removed**

Also, are you using the schematic in this: **broken link removed**?

Cheers,
 

Yes, i'm using schematic from that site.

i've tried MTK and i get same kind of result.

this is my breadboard ... maybe i did something wrong and cant see it anymore ...

94_1170533085.jpg


Left bottom IC is max232 and right one is 74hc125.
All of the capacitors are 1uF except those for xtal which are 22pF.

Thanx!
 

Didn't see your serial cable. Make sure you connect the MAX232 to PC correctly.

You did not follow the Maxim's schematic. /EA should be asserted before asserting RST and /PSEN (don't use the buffer for /EA). Pin 9 of HC125 should be grounded (for /PSEN).

Cheers,
 

Sorry for this long reply ... i had no time to check what you've suggested ...
Still doesnt work ... and i have no idea why. With multimeter i get proper voltages on proc, rs232 and 74hc125. I was try to reconnect everything again, but with no luck either ... i'm sending 2 images of breadboard with rs232 connector, if you can see what is wrong.

38_1171557310.jpg


25_1171557248.jpg
 

You are missing the connection from pin 9 of MAX232 to pin 1 and 4 of HC125.

You have got wrong connections:
pin 12 of MAX232 to pin 11 of DS89C420 instead of pin 10
pin 11 of MAX232 to pin 12 of DS89C420 instead of pin 11

Also, crystal should be close to pin 18 and 19.

Cheers,
 

You are missing the connection from pin 9 of MAX232 to pin 1 and 4 of HC125.
Click to expand...
Ok, i've connected pin9 to pin1 and pin4

You have got wrong connections:
pin 12 of MAX232 to pin 11 of DS89C420 instead of pin 10
pin 11 of MAX232 to pin 12 of DS89C420 instead of pin 11
Click to expand...

are you sure about this ? in datasheet it said that RXD0 is on pin 10 and TXD0 is on pin 11.

Also i've moved crystall near the osc pins of ds89c420.

Still get:
Unable to establish communication with target.
Check connection to target system or consult help files.

Tried every baud rate ... but with no luck ... I've 2 of those chips, but get same result with both of them ...
 

ScOe said:
You have got wrong connections:
pin 12 of MAX232 to pin 11 of DS89C420 instead of pin 10
pin 11 of MAX232 to pin 12 of DS89C420 instead of pin 11
Click to expand...

are you sure about this ? in datasheet it said that RXD0 is on pin 10 and TXD0 is on pin 11.
Click to expand...

That's why I said you've got wrong connections: You are connecting pin 12 of MAX232 to pin 11 of DS89C420 (this should be pin 10 of DS89C420, RXD0), and you are connecting pin 11 of MAX232 to pin 12 of DS89C420 (this should be pin 11 of DS89C420, TXD0).

Cheers,
 

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