HD64F3437TF16 Datasheet, PDF (175/752 Pages) Hitachi Semiconductor – 12 V must not be applied to the S-mask model (single-power-supply specification), as this may permanently damage the device.

7.11 Port A
7.11.1 Overview
Port A is an 8-bit input/output port that is multiplexed with key-sense input pins. The port A pin
functions are the same in all operating modes. Figure 7.18 shows the pin configuration of port A.
Port A has built-in, programming MOS input pull-up transistors.
Pins in port A can drive one TTL load and a 90-pF capacitive load. They can also drive a
darlington transistor. Pins PA₄, PA₅, PA₆, and PA₇ can be driven as bus buffers, as shown in
section 13, I²C Bus Interface.
Port A
Port A pins
PA₇ (input/output)/KEYIN₁₅ (input)
PA₆ (input/output)/KEYIN₁₄ (input)
PA₅ (input/output)/KEYIN₁₃ (input)
PA₄ (input/output)/KEYIN₁₂ (input)
PA₃ (input/output)/KEYIN₁₁ (input)
PA₂ (input/output)/KEYIN₁₀ (input)
PA₁ (input/output)/KEYIN₉ (input)
PA₀ (input/output)/KEYIN₈ (input)
Figure 7.18 Port A Pin Configuration
7.11.2 Register Configuration and Descriptions
Table 7.20 summarizes the port A registers.
Table 7.20 Port A Registers
Name
Abbreviation Read/Write Initial Value Address
Port A data direction register PADDR
W
H'00
H'FFAB
Port A output data register
PAODR
R/W
H'00
H'FFAA
Port A input data register
PAPIN
R
Undetermined H'FFAB
Note: The data direction register (PADDR) and input data register (PAPIN) have the same
address.
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