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legnumvr4
United Kingdom
4 Posts |
 Posted - 08/30/2008 : 10:29:57
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Hi,
I have been trying to read (first!) and write an ST eeprom with the following no.s written on it:
93C46CB3
93A631
MAL
ST (logo)
I believe it to be a Microwire compatible eeprom so I purchases a simple eeprom programmer on eBay from this place:
It is supplied with the Ponyprog software.
Anyway, I have connected the 93Cxx ZIF socket connections via wires and sub-miniature probe clips to the legs of the chip.
Now when I try to read the chip I get spurious readings. Sometimes the display shows a few values, then if I read again I get a few more. If I read 4 or 5 times in quick succession then I get all 'FF'. What is going on? I'm obviously getting something because if I disconnect a pin I get nothing.
So I have come to the assumption that the eeprom programmer does not work or is not suitable.
I want to know if the Dual Power Willem Universal EPROM Programmer advertised on MCUMall would work better?
Thanks, Phil |
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| Reply #1
ZLM
2945 Posts |
Posted - 08/30/2008 : 16:03:16
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All those programmers are designed for programming EEPROM in ZIF socket. The in-circuit-programming are not guaranteed since the programmer is not designed for programming that way. It is pretty much depending on the EEPROM circuit. The programmer only provide guaranteed power for a single chip. Not for the EEPROM surrounding circuit. So, this is why some programming do not work.
Also, the wires you connect the programmer to chip may not meet the signal requirement. The signal may distorted when it reach the chip from the programmer.
You may need a in-circuit-programming driver. Like this one:
http://www.mcumall.com/comersus/store/comersus_viewItem.asp?idProduct=4310
However, this adapter is not designed for 93CXXX EEPROM. It is designed for mother board BIOS in-circuit-programming.
There are many user reported they successuly in circuit programmed EERPOM by Willem programmer. But this does not mean it 100% works in your case.
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| Reply #2
legnumvr4
United Kingdom
4 Posts |
Posted - 09/01/2008 : 13:38:44
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ZLM, thanks for the info. Following your suggestion I googles around a bit. It seems that in-circuit programming (or is that ISP?) of 93c46 eeproms is not so simple as I had hoped.
I am trying to read a car airbag module.
I came across two possible problems/solutions:
I have to supply the eeprom with a low voltage to avoid interference from other parts or the microcontroller:
Or I have to connect a MCU Reset Line (RST) (presuambly to the microcontroller chip not the eeprom??) somehow:
www.kanda.com/datasheet/serialwb.pdf
As you can see both these options are $$$ and a therefore a no-go (I might as well pay for a new airbag unit).
So, could the Willem Eeprom programmer be modified to achieve either (or both) these solutions? Is the voltage to Vcc adjustable - would a simple resistor in-line with the chip Vcc leg work? I don't know what voltage would be needed but I guess I could experiment. How could I create a RST signal?
Sorry for the newbie questions but I'm quickly getting out of my depth here!
Thanks. |
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| Reply #3
ZLM
2945 Posts |
Posted - 09/01/2008 : 23:13:17
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The simplest way to read/write the chip is to remove the chip from the PCB and put it on the programmer. This way is 100% guaranteed working.
For the RESET signal on Microprocessor, most likely you need read the Microprocessor datasheet and find the RST pin on the Microprocessor. Then apply a voltage(hi or lo) on that pin.
The True-USB Willem will adjust the Vcc voltage automatically. So, you do not need set the voltage manually.
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In-circuit eeprom programming of 93C46CB3
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