Table of Contents
Advertisement
Port 8 Data Direction Register (P8DDR): P8DDR is an 8-bit write-only register that can select
input or output for each pin in port 8.
Bits 7 to 5 are reserved. They are fixed at 1, and cannot be modified.
Bit
Initial value
Modes
1 to 4
Read/Write
Initial value
Modes
5 to 7
Read/Write
Modes 1 to 5 (Expanded Modes): When bits in P8DDR bit are set to 1, P8
CS
output pins. When bits in P8DDR are cleared to 0, the corresponding pins become input ports.
3
However, P8
can also be used as an output port, depending on the setting of bits DRAS2 to
1
DRAS0 in DRAM control register A (DRCRA). For details see section 6.5.2, DRAM Space and
RAS Output Pin Settings.
In modes 1 to 4 (expanded modes with on-chip ROM disabled), following a reset P8
the CS
output, while CS
0
enabled), following a reset CS
When the refresh enable bit (RFSHE) in DRCRA is set to 1, P8
RFSHE is cleared to 0, P8
details see table 8.14.
Mode 6 and 7 (Single-Chip Mode): Port 8 is a generic input/output port. A pin in port 8 becomes
an output port if the corresponding P8DDR bit is set to 1, and an input port if this bit is cleared to
0.
P8DDR is a write-only register. Its value cannot be read. All bits return 1 when read.
P8DDR is initialized to H'F0 in modes 1 to 4, and to H'E0 in modes 5 to 7, by a reset and in
hardware standby mode. In software standby mode P8DDR retains its previous setting. Therefore,
if a transition is made to software standby mode while port 8 is functioning as an input/output port
and a P8DDR bit is set to 1, the corresponding pin maintains its output state.
7
6
5
1
1
1
1
1
1
Reserved bits
to CS
are input ports. In mode 5 (expanded mode with on-chip ROM
1
3
to CS
are all input ports.
0
3
becomes an input/output port according to the P8DDR setting. For
0
4
3
P8 DDR
P8 DDR
P8 DDR
4
3
1
0
W
W
0
0
W
W
Port 8 data direction 4 to 0
These bits select input or
output for port 8 pins
is used for RFSH output. When
0
Rev. 4.00 Jan 26, 2006 page 297 of 938
Section 8 I/O Ports
2
1
0
P8 DDR
P8 DDR
2
1
0
0
0
0
W
W
W
0
0
0
W
W
W
become CS
to P8
4
1
functions as
4
REJ09B0276-0400
to
0
Advertisement
Table of Contents
