Fujitsu MB89202, F202RA manual Registers of Port 4 PDR4, Functions of Port 4 Registers

CHAPTER 4 I/O PORTS

4.4.1Registers of Port 4 (PDR4)

This section describes the registers associated with port 4.

■Functions of Port 4 Registers

●Port 4 data register (PDR4)

The PDR4 register indicates the state of the pins. For a pin set to function as an output port, the same value

("0"or "1") as held by the output latch can be read from this register. If the pin is set to function as an input

port, however, its output latch value cannot be read from the register.

Note:

When a bit manipulation instruction (SETB, CLRB) is executed, the output latch values, not the value states of the pins, are read; thus, output latch values, excepting those for bits to be manipulated, do not change.

Table 4.4-3lists the functions of the port 4 registers.

Table 4.4-3	Functions of Port 4 Registers
Register	Data	When being read		When being written	Read/	Address	Initial
name					Write		value
				Output latch of "0" is set and
	0	Pin state is "L" level.		"L" level is output to the pin
				in output port mode.
Port 4
				Output latch of "1" is set and
data			N-ch open-
				the pin in output port mode	R/W	000FH	----XXXXB
register		Pin state	drain type
(PDR4)				is set at Hi-Z.
	1	is "H"
			CMOS	Output latch of "1" is set and
		level.
			push-pull	"H" level is output to the pin
			type	in output port mode.
Port 4				The pin is set to function as
	0	Input port pin		input pin with output
data				transistor operation disabled.	R/W	0010H
direction							----0000B
				The pin is set to function as
register
(DDR4)	1	Output port pin		output pin with output
				transistor operation enabled.
Port 4	0	N-ch open-drain type		Output format of the pin is
output				set to N-ch open-drain type.
format					R/W	0011H	----0000B
				Output format of the pin is
setting
register	1	CMOS push-pull type		set to CMOS push-pull type.
(OUT4)

R/W : Readable and Writable

X : Undefined

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