C509-L_97 Datasheet, PDF (88/290 Pages) Siemens Semiconductor Group – 8-Bit CMOS Microcontroller

On-Chip Peripheral Components
C509-L
6.1.1.3 Bidirectional (CMOS) Port Structure
6.1.1.3.1 Input Mode
Figure 6-7 shows the bidirectional port structure in the input mode.
Figure 6-7
Bidirectional Port Structure - Input Mode
The input mode for a port pin is selected by programming the corresponding direction bit to '1'
(QDL='1'). The FETs p1, p2, p3 and n1 are switched off. Through a Schmitt-Trigger, designed to
detect CMOS levels, the input signal is lead to the internal bus where it can be read by the
microcontroller.
Semiconductor Group
6-10
1997-10-01