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Chapter 2 Port Integration Module (S12XEPIMV1)
MC9S12XE-Family Reference Manual Rev. 1.07
Freescale Semiconductor
107
2.3.11
Port E Data Register (PORTE)
2.3.12
Port E Data Direction Register (DDRE)
Address 0x0008 (PRR)
Access: User read/write
1
1
Read: Anytime. In emulation modes, read operations will return the data from the external bus, in all other modes the data
source is depending on the data direction value.
Write: Anytime. In emulation modes, write operations will also be directed to the external bus.
2
These registers are reset to zero. Two bus clock cycles after reset release the register values are updated with the associated
pin values.
7
6
5
4
3
2
1
0
R
PE7
PE6
PE5
PE4
PE3
PE2
PE1
PE0
W
Altern.
Function
XCLKS
or
ECLKX2
MODB
or
TAGHI
MODA
or
RE
or
TAGLO
ECLK
EROMCTL
or
LSTRB
or
LDS
RW
or
WE
IRQ
XIRQ
Reset
0
0
0
0
0
0
—
2
—
2
= Unimplemented or Reserved
Figure 2-9. Port E Data Register (PORTE)
Table 2-11. PORTE Register Field Descriptions
Field
Description
7-0
PE
Port E general purpose input/output data
—Data Register
Port E bits 7 through 0 are associated with external bus control signals and interrupt inputs. These include mode
select (MODB, MODA), E clock, double frequency E clock, Instruction Tagging High and Low (TAGHI, TAGLO),
Read/Write (RW), Read Enable and Write Enable (RE, WE), Lower Data Select (LDS), IRQ, and XIRQ.
When not used with the alternative functions, Port E pins 7-2 can be used as general purpose I/O and pins 1-0 can
be used as general purpose inputs.
If the associated data direction bits of these pins are set to 1, a read returns the value of the port register, otherwise
the buffered pin input state is read.
Pins 6 and 5 are inputs with enabled pull-down devices while RESET pin is low.
Pins 7 and 3 are inputs with enabled pull-up devices while RESET pin is low.
Address 0x0009 (PRR)
Access: User read/write
1
7
6
5
4
3
2
1
0
R
DDRE7
DDRE6
DDRE5
DDRE4
DDRE3
DDRE2
0
0
W
Reset
0
0
0
0
0
0
0
0
= Unimplemented or Reserved
Figure 2-10. Port E Data Direction Register (DDRE)