Port Integration Module (S12GPIMV1)
MC9S12G Family Reference Manual Rev.1.27
242 NXP Semiconductors
2.5.2.3 Data Direction Register (DDRx)
This register defines whether the pin is used as an general-purpose input or an output.
If a peripheral module controls the pin the contents of the data direction register is ignored (Figure 2-64).
Independent of the pin usage with a peripheral module this register determines the source of data when
reading the associated data register address (2.5.2.1/2-241).
NOTE
Due to internal synchronization circuits, it can take up to 2 bus clock cycles
until the correct value is read on port data or port input registers, when
changing the data direction register.
Figure 2-64. Illustration of I/O pin functionality
2.5.2.4 Pull Device Enable Register (PERx)
This register turns on a pullup or pulldown device on the related pins determined by the associated polarity
select register (2.5.2.5/2-242).
The pull device becomes active only if the pin is used as an input or as a wired-or output. Some peripheral
module only allow certain configurations of pull devices to become active. Refer to Section 2.3, “PIM
Routing - Functional description”.
2.5.2.5 Pin Polarity Select Register (PPSx)
This register selects either a pullup or pulldown device if enabled.
It becomes only active if the pin is used as an input. A pullup device can be activated if the pin is used as
a wired-or output.
PT
DDR
output enable
module enable
1
0
1
1
0
0
PIN
PTI
data out
Module
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