Solving ISP Problems

Started by admin, April 11, 2003, 04:12:42 PM

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Andy Ayre

We have just added Flash Magic Application Note 4, which details steps that can be taken to try and resolve ISP problems. It is available from the bottom of the Flash Magic page.


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        I am soham from pune.Currently I am working on GagePort in which
we are using 89C668.While programming the controller first time I enter a small test program.The test program is working properly.But now I can't
reprogram the controller.It is giving the error message as"com port not
connected try with higher/lower Baudrate.It is not performing blank check,
check security bits and etc.I am using Flash Magic 1.7 .Please suggest me the solution.

Andy Ayre

The most common reason why someone can program a device fine the first time and then be unable to program it, is that you are not entering ISP mode correctly. The device comes from the factory in ISP mode, so when you attempt to program the device for the second time, that is the the first time you are really testing getting into ISP mode.

Check the voltages on ALE, /PSEN, P2.6 and P2.7 are all what they should be according to the current datasheet. Don't forget that you need to pull BOTH P2.6 and P2.7 high during reset - missing off one of those pins is a common mistake.

If this doesn't help then read Flash Magic Application Note 4 - it will hopefully lead you to the answer. If it does not, the very last section titled "last resort" will enable me to work out the problem. But you need to following the previous steps in that application note first.

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Greg Watkin

In your note of 4-30-03, it was mentioned that both P2.6 and P2.7 must be held high during reset. I noticed in the Philips Application note that it say that "P2.6 and P2.7 are high or floating" and "ALE is high or floating". Do you know if these pins MUST be held high, or just that they can't be pulled low? I would be very interested in any experience anybody has had with this.


Dear friend,
1. Iam first time user of your of flash device. we are not having programmer for this device.

2. we tried with your latest version of  ISP software . In philps data book it is given p2.7 to be connected to high  ,your application note  it is given p2.6 and p2.7 to pulled high during the reset.

3. request let me know which are the pins to be used while programming and the hardware to be used.

Thannking you.

Andy Ayre


They can be left floating, but I prefer to pull them high. I've personally never had any problems when pulling them high. Note that I have never left them floating to be able to tell you if there are any problems doing that. A floating pin could be affected by EMI or noise in the circuit, so I prefer to make sure the voltage on the pin is well within what is required and stable.

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Andy Ayre


The latest versions of the Rx2Hxx/66x datasheet and Philips Application Note AN461 contain the pins to be used.

At the falling edge of RESET:

PSEN = low
EA = higher than VIH
P2.6 = high (or floating)
P2.7 = high (or floating)
ALE = high (or floating)

VIH = input high voltage allowed on port pins and EA. The minimum allowed for VIH is 0.2VCC + 0.9. So in a 5V system, VIH must be higher than 1.9V.

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