9.3 Port 2
9.3.1 Overview
Port 2 is an 8-bit input/output port with the pin configuration shown in figure 9-2. The pin
functions differ according to the operating mode.
In modes 1 to 4 (expanded modes with on-chip ROM disabled), port 2 consists of address bus
output pins (A
15
to A
8
). In modes 5 and 6 (expanded modes with on-chip ROM enabled), settings
in the port 2 data direction register (P2DDR) can designate pins for address bus output (A
15
to A
8
)
or generic input. In mode 7 (single-chip mode), port 2 is a generic input/output port.
When DRAM is connected to area 3, A
9
and A
8
output row and column addresses in read and
write cycles. For details see section 7, Refresh Controller.
Port 2 has software-programmable built-in pull-up MOS. Pins in port 2 can drive one TTL load
and a 90-pF capacitive load. They can also drive a darlington transistor pair.
Figure 9-2 Port 2 Pin Configuration
Port 2
P2 /A
P2 /A
P2 /A
P2 /A
P2 /A
P2 /A
P2 /A
P2 /A
7
6
5
4
3
2
1
0
15
14
13
12
11
10
9
8
P2 (input/output)
P2 (input/output)
P2 (input/output)
P2 (input/output)
P2 (input/output)
P2 (input/output)
P2 (input/output)
P2 (input/output)
7
6
5
4
3
2
1
0
A (output)
A (output)
A (output)
A (output)
A (output)
A (output)
A (output)
A (output)
15
14
13
12
11
10
9
8
Port 2 pins
Mode 7
Modes 1 to 4
P2 (input)/A (output)
P2 (input)/A (output)
P2 (input)/A (output)
P2 (input)/A (output)
P2 (input)/A (output)
P2 (input)/A (output)
P2 (input)/A (output)
P2 (input)/A (output)
7
6
5
4
3
2
1
0
Modes 5 and 6
15
14
13
12
11
10
9
8
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