Spin Semiconductor

I had problem with FV-1 not reading the correct program from external eeprom. I tested the circuit by setting FV-1 to read from an external eeprom starting from program 1 to program 8 ( the eeprom contains 8 distinct programs), and here's the result :

Program Adress_|_Program read by FV-1
___ 000 ____________ Program #1______<-- OK
___ 001 ____________ Program #2______<-- OK
___ 010 ____________ Program #1______<-- WRONG ( should be Program #3 )
___ 011 ____________ Program #2______<-- WRONG ( should be Program #4 )
___ 100 ____________ Program #5______<-- OK
___ 101 ____________ Program #6______<-- OK
___ 110 ____________ Program #5______<-- WRONG ( should be Program #7 )
___ 111 ____________ Program #6______<-- WRONG ( should be Program #8 )

I check the voltage on FV-1's program address pins and they are correct. Looking at the result it seems that the 2nd address bit is always read as '0' by FV-1 internally, regardless of the actual voltage on the pin. I replaced the EEPROM just to be sure that it's not caused by faulty EEPROM, the same problem remains.

I only had this problem with the 6th board that I've built. Am I having a faulty FV-1 chip?

I've never seen that error before. The chips are all tested and run through 8 external programs to check loading, etc. I would carefully check for a solder bridge possibly under the chip or other reason why the chip thinks the pin is low.

Found the source of the problem, it was a fault somewhere on the board that intermittently shorting the S1 pin to the ground. Thanks Frank.

Glad you found it, those intermittent ones can be a real pain to find.