HD404328 Datasheet, PDF (45/96 Pages) Hitachi Semiconductor – 4 BIT SINGLE CHIP MICROCOMPUTER

HD404328 Series
Port mode register C (PMRC): $012
3
2
1
0
Initial value: 0000, R/W: W
BUZZ output frequency selection
R1₃/BUZZ pin mode selection
Pull-up MOS transistor on/off selection
PMRC
Bit 3
0
1
Pull-Up MOS
On/Off Selection
Off
On
PMRC
Bit 3
0
1
Port
Selection
R1₃
BUZZ
LCD output register (LOR): $015
3
2
1
0
Initial value: 0000, R/W: W
R2/SEG1–SEG4 pin mode selection
R3/SEG5–SEG8 pin mode selection
R4/SEG9–SEG12 pin mode selection
R5/SEG13–SEG16 pin mode selection
LOR
Bit 3
Port
Selection
LOR
Bit 2
Port
Selection
LOR
Bit 1
Port
Selection
LOR
Bit 0
Port
Selection
0
R5
0
R4
0
R3
0
R2
1 SEG13–SEG16 1 SEG9–SEG12 1 SEG5–SEG8 1 SEG1–SEG4
Figure 24 I/O Switching Mode Registers (cont)
Pull-Up MOS Transistor Control: A program-controlled pull-up MOS transistor is provided for each
input/output pin. The on/off status of all these transistors is controlled by bit 3 of port mode register C
(PMRC), and the on/off status of an individual transistor can also be controlled by the port data register of
the corresponding pin—enabling on/off control of that pin alone.
The on/off status of each transistor and the peripheral function mode of each pin can be set independently.
The configuration of the I/O buffer is shown in figure 25, and the configurations of various program-
controlled I/O circuits are given in table 23.
How to Deal with Unused I/O Pins: I/O pins that are not needed by the user system (floating) must be
connected to V_CC to prevent LSI malfunctions due to noise. These pins must either be pulled up to V_CC by
their pull-up MOS transistors or by resistors of about 100 kΩ.
43