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Best Practices for EPROM IC Chip Programming

(4) Reading a Master Chip
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When we are given a master IC chip from a customer to make volume copies, we handle it very carefully, especially if it is one of a kind. Here are the steps we take. Hope they will help you when you need to read from IC chips that contain critical data.

(A) Test the setup with one of our own IC chips before touching the master.

After we have set up the equipment and selected the appropriate device from the s/w, we put in one of OUR OWN devcies and make sure it is read with no problem. The reason is because equipment can fail, software can have bugs, and human beings can make mistakes. Even though these chances are extremely slim, it is wise to take the precautions because losing the master can be catastrophic to the customer.

(B) Read the master

VERY carefully, we click the [Read] icon, making sure that the mouse is not moving too fast and went to the [Program] icon].

(C) Save the data into a file

After the master has been read, we note the checksum.

Suppose the master is labeled as U17 by the customer, and suppose the part # is 27C010 and the checksum is 1234 (taking the last 4 digits if it is an 8-digit checksum), then we save the data immediately into a data file named:


(D) Verify against the master

Then we verify the buffer against the master chip, to make sure that reading from the master is consistent. If it does not verify, it may mean that (in the case of EPROMs) some bits in the master may have been partially erased, or that the master was not programmed properly in the first place. (If you encounter this, contact us for possible solutions.)

(E) Then we put the master away properly.

(F) Check the data buffer

After the data has been saved and the master put away, now is the time to look at the data buffer. We follow this sequence to eliminate the possibility of accidentally modifying the buffer before saving the data.

Clicking the [Buffer] icon would display the data in the buffer.

For memory chips or micros, a typical data pattern would be like this:

If you see all FFs, 00s, or all bytes of the same value, then something is wrong.
For micros, it could be secured or locked and there will be no way to read the content.

(Conventional EPROMs and parallel memories cannot be secured. Most serial PROMs and EEPROMs cannot be secured except some new 25xx series serial EEPROMs.)

For logic devices, if it is not secvured, the buffer should contain a mixture of 1s and 0s. If it contains all 1s or all 0s, then it is secured.

If the master is secured, then the content of the data buffer or the data file cannot be used to make copies.

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