
23.0.5.2
Port B Data Register (PORTB)
Read: Anytime.
Write: Anytime.
23.0.5.3
Port A Data Direction Register (DDRA)
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.
Table 23-4. PORTA Field Descriptions
Field
Description
7–0
PA[7:0]
Port A — Port A pins 7–0 are associated with address outputs ADDR15 through ADDR8 respectively inexpanded
modesWhen this port is not used for external addresses, these pins can be used as general purpose I/O. If the
data direction bits of the associated I/O pins are set to logic level “1”, a read returns the value of the port register,
otherwise the buffered pin input state is read.
7
6
5
4
3
2
1
0
R
PB7
PB6
PB5
PB4
PB3
PB2
PB1
PB0
W
Reset
0
0
0
0
0
0
0
0
Figure 23-4. Port B Data Register (PORTB)
Table 23-5. PORTB Field Descriptions
Field
Description
7–0
PB[7:0]
Port B
— Port B pins 7–0 are associated with address outputs ADDR7 through ADDR1 respectively in expanded
modes. Pin 0 is associated with output ADDR0 in emulation modes and special test mode and with Upper Data
Select (UDS) in normal expanded mode. When this port is not used for external addresses, these pins can be
used as general purpose I/O. If the data direction bits of the associated I/O pins are set to logic level “1”, a read
returns the value of the port register, otherwise the buffered pin input state is read.
7
6
5
4
3
2
1
0
R
DDRA7
DDRA6
DDRA5
DDRA4
DDRA3
DDRA2
DDRA1
DDRA0
W
Reset
0
0
0
0
0
0
0
0
Figure 23-5. Port A Data Direction Register (DDRA)