Which registers can I trash with user-defined bank switching?

Using C51 (v6.xx/7.xx) with user defined bank switching (mode 4), which registers must be preserved on the call and return? R1-R7 must be preserved on the call & return, since these pass parameters...
Which registers can I trash with user-defined bank switching?

Using C51 (v6.xx/7.xx) with user defined bank switching (mode 4), which registers must be preserved on the call and return? R1-R7 must be preserved on the call & return, since these pass parameters...
how to manipulate values at the ports

can i manipulate the values at the port pins individually,, i.e., if i want the 6th pin of port0 to be high, can i assign 1 to that particular pin, without disturbing the other port pin values??...
how to manipulate values at the ports

can i manipulate the values at the port pins individually,, i.e., if i want the 6th pin of port0 to be high, can i assign 1 to that particular pin, without disturbing the other port pin values??...
Problem with a simple vector manipulation! Help!

Hi. I'm using Phytec KC-161 eval board. During my project i found a a problem with vectors. So i tried to monitor the values of a simple unsigned int vector[6] after I initialize it. And i saw that the...