XC886/888CLM
Parallel Ports
User’s Manual
6-3
V1.3, 2010-02
Parallel Ports, V 1.0
Figure 6-1
General Structure of Bidirectional Port
shows the structure of an input-only port pin. Each P2 pin can only function
in input mode. Register P2_DIR is provided to enable or disable the input driver. When
the input driver is enabled, the actual voltage level present at the port pin is translated
into a logic 0 or 1 via a Schmitt-Trigger device and can be read via the register P2_DATA.
Each pin can also be programmed to activate an internal weak pull-up or pull-down
device. Register P2_PUDSEL selects whether a pull-up or the pull-down device is
Px_OD
Open Drain
Control Register
Px_Data
Data Register
Internal Bus
AltDataOut 2
Px_ALTSEL0
Alternate Select
Register 0
Px_ALTSEL1
Alternate Select
Register 1
AltDataIn
Pin
Px_PUDEN
Pull-up/Pull-down
Enable Register
Px_PUDSEL
Pull-up/Pull-down
Select Register
AltDataOut1
Pad
Out
In
Output
Driver
Input
Driver
00
Schmitt Trigger
enable
enable
Pull
Up
Device
Pull
Down
Device
VDDP
enable
enable
Px_DIR
Direction Register
01
10
AltDataOut 3
11
*