Using port 4 in the P87C51MC2 (extended memory chip from Philips)

Hi,
I'm unable to reset the pin P4.1(TXD1)on target though it's possible on the simulator.
The register setting I'm doing are as follows:

SPCTL = 0x00; //not bit addressable.
TXD1 = 0; // P4 is bit addressable.

I also tried enabling SPCTL.6 and SPCTL.7(this pin tells the SPI logic, not to use the SS-pin (P4.1) and make it available as standard I/O) before writing a '0' to P4.1 but was unsuccessul.

As I said earlier, on the simulator, I can see that port pin is reset while on the target, it is always set.

Why is the behaviour different on the target and simulator for the same code?

Any help would be appreciated.

Warm regards,
Sandy