ADuC812 i2c eeprom memory simulation problem

I am trying to simulate i2c eeprom memory using signal function from http://www.keil.com/support/docs/3325.htm and code from http://www.keil.com/i2c/examples.asp (ADU812_I2C.ZIP). It seems that the signal function receives correct address byte, but the simulator doesn't seem to receive the ACK. It looks like the write to the I2C_IN (0xFF00) is completely ignored, and MDI has the value of 1 (NACK).
Of course I have changed the SADR variable to 0x50.
Is this behaviour intended? Maybe I'm doing something wrong, I'm relatively new to Keil

Thank you in advance,
Alex

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