My problem is the serial interface. Unfortunately characters send to the 8052 are lost, because the processor is busy somewhere else in the program.
The easiest thing to do would be to give the serial interrupt a high priority, and stuff the bytes received into a fifo, but then the processing of the serial data might too late and the buffer would overflow.
Is it possible to somehow trigger a low level interrupt within the high level serial interrupt, which then deals with the serial data a soon as possible while still being interruptible by the high level interrupts?