Alternative port-pin functions
The AT89S8252 ports have alternative functions.
The following table shows the alternative functions.

Port pin Alternate function
P1.0 T2 external count input to timer.counter 2, clock out
P1.1 T2EX timer/counter 2 capture/reload trigger and direction flag
P1.4 /SS Slave port select input
P1.5 MOSI Master data output, slave data input pin for SPI channel
P1.6 MISO Master data input, slave data output pin for SPI channel
P1.7 SCK Master clock output, slave clock input pin for SPI channel
P3.0 RxD serial input port
P3.1 TxD serial output port
P3.2 /INT0 external interrupt 0
P3.3 /INT1 external interrupt 1
P3.4 T0 timer 0 external input
P3.5 T1 timer 1 external input
P3.6 /WR external data memory write strobe
P3.7 /RD external data memory read strobe
/ means active low