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Chapter 3 Port Functions
46
Port Control Registers
■ Port Output/Input Mode Registers
• PnOMD/PnIMD registers
These register settings determine whether the port pins(P10 to P14, PA0 to PA5) are used
as I/O ports or as special function pins (dual function).
If the special (dual) functions used, the PnDIR, PnPLU, PnPLUD, and other registers
must be set.
■ Pin Control Registers
• FLOAT1 registers
This register specifies whether the resistors-attached to pins P7 and PA are pull-up
resistors or pull-down resistors.
In addition, this register selects either zero cross input or Schmitt trigger input for pin
P21.
Figure 3-2-2 Pin Control Register 1(FLOAT1: X'03F4B',R/W)
0
1
I/O port
Special function pin
Setting the PAIMD register
prevents unnecessary current
from flowing in a pin when an
intermediate voltage (analog
voltage) is applied to the pin.
0
1
Schmitt trigger input
P21 input mode selection
SENS input
P21IM
0
1
pull-up resistor
PA pull-up/pull-down
resistor selection
pull-down resistor
PARDWN
01245673
(at reset: -----000)
FLOAT1
P7RDWNPARDWNP21IM
0
1
pull-up resistor
P7 pull-up/pull-down
resistor selection
pull-down resistor
P7RDWN