Chapter 4 Port Integration Module (S12XDP512PIMV2)
MC9S12XDP512 Data Sheet, Rev. 2.11
Freescale Semiconductor 205
4.3.2.10 Port E Data Direction Register (DDRE)
Read: Anytime. In emulation modes, read operations will return the data from the external bus, in all other
modes the data are read from this register.
Write: Anytime. In emulation modes, write operations will also be directed to the external bus.
0x0009 (PRR)
76543210
R
DDRE7 DDRE6 DDRE5 DDRE4 DDRE3 DDRE2
00
W
Reset 00000000
= Unimplemented or Reserved

Figure 4-12. Port E Data Direction Register (DDRE)

Table 4-13. DDRE Field Descriptions

Field Description
7–0
DDRE[7:2]
Data Direction Port E — his register controls the data direction for port E. When Port E is operating as a general
purpose I/O port, DDRE determines whether each pin is an input or output. A logic level “1” causes the
associated port pin to be an output and a logic level “0” causes the associated pin to be a high-impedance input.
Port E bit 1 (associated with IRQ) and bit 0 (associated with XIRQ) cannot be configured as outputs. Port E, bits
1 and 0, can be read regardless of whether the alternate interrupt function is enabled.
0 Associated pin is configured as input.
1 Associated pin is configured as output.
Note: Due to internal synchronization circuits, it can take up to 2 bus clock cycles until the correct value is read
on PORTE after changing the DDRE register.