80C186EC/80C188EC Microprocessor User's Manual

INPUT/OUTPUT PORTS
Register Name:
Register Mnemonic:
Register Function:
Port Control Register
PxCON (P1CON, P2CON, P3CON)
Selects port or peripheral function for a port pin.
15 0
P
C
7
P
C
6
P
C
5
P
C
4
P
C
3
P
C
2
P
C
1
P
C
0
A1312-0A
Bit
Mnemonic
Bit Name
Reset
State
Function
PC7:0
Port Control
7:0
FFH
When the PC bit for a specific pin is set, the
associated integrated peripheral controls both
pin direction and pin data. Clearing the PC bit
makes the pin a general-purpose I/O port.
NOTE: PC7 and PC6 do not exist for Port 3.
NOTE:
Reserved register bits are shown with gray shading. Reserved bits must be written
to a logic zero to ensure compatibility with future Intel products.
Figure 13-4. Port Control Register (PxCON)
13.2.2 Port Direction Register
The Port Direction Register (Figure 13-5) controls the direction (input or output) for each pin programmed
as a general-purpose I/O port. The Port Direction bit has no effect on output-only port
pins. These unused direction control bits can be used for bit storage.
The Port Direction Register is read/write. When read, the register returns the value written to it
previously. Pins with their direction fixed return the value in this register, not a value indicating
their true direction. The direction of a port pin assigned to a peripheral function is controlled by
the peripheral; the Port Direction value is ignored.
13-8