Department of Computer Scien

ce and Information Engineering

National Cheng Kung University, TAIWAN

I/O HANEL

PROGRAMMINGPort 2 as Input or Dual Role

‰To make port 2 an input port, it must be programmed as such by writing 1 to all its bits‰In many 8051-based system, P2 is used as simple I/O‰In 8031-based systems, port 2 must be used along with P0 to provide the 16-bit address for the external memory

¾Port 2 is also designated as A8

– A15,

indicating its dual function¾Port 0 provides the lower 8 bits via A0

– A7

P1.0P1.1P1.2P1.3P1.4P1.5P1.6P1.7RST(RXD)P3.0(TXD)P3.1(INT0)P3.^2 (I^3 NT1)P3.(T0)P3.4(T1)P3.5(WR)P3.6(RD)P3.7XTAL2XTAL1GND

VccP0.0(AD0)P0.1(AD1)P0.2(AD2)P0.3(AD3)P0.4(AD4)P0.5(AD5)P0.6(AD6)P0.7(AD7)-EA/VPPALE/PROG-PSENP2.7(A15)P2.6(A14)P2.5(A13)P2.4(A12)P2.3(A11)P2.2(A10)P2.1(A9)P2.0(A8)

(^1234567891011121314151617181920)
(^40393837363534333280513130) (8031) 292827262524232221