NEC PD78P214 Manuale Utente
74
µ
PD78214 Sub-Series
(3) Control signal input or output
Regardless of setting of the port mode 3 register (PM3), each bit of port 3 can be used to input or output a
control signal, independently of the other bits, by setting the corresponding bit of the port mode control
register (PMC3) to 1. When a pin is used for a control signal, executing a read instruction for the port can detect
the state of the control signal.
control signal, independently of the other bits, by setting the corresponding bit of the port mode control
register (PMC3) to 1. When a pin is used for a control signal, executing a read instruction for the port can detect
the state of the control signal.
Fig. 5-18 Port Specified as a Control Signal Input or Output
(a) Control signal output
When a bit of the port mode register (PM3n) is 1, executing a read instruction for port 3 can read the level
of the corresponding control signal pin.
of the corresponding control signal pin.
When a bit of the port mode register (PM3n) is 0, executing a read instruction for port 3 can check the
corresponding control signal in the
corresponding control signal in the
µPD78214.
Remark For bit 3 (P33) of port 3, “SB0” is a reserved word in the NEC assembly program package. The bit is also defined in a header
file named sfrbit.h by the C compiler.
(b) Control signal input
Only when a bit of the port mode register (PM3n) is 1, executing a read instruction for port 3 can read the
level of the corresponding control signal pin.
level of the corresponding control signal pin.
5.4.4 Built-In Pull-Up Resistor
Port 3 has built-in pull-up resistors. When port 3 must be pulled up, the built-in pull-up resistors should be used.
Use of the built-in pull-up resistors can reduce the number of the required components and the required
installation space.
Use of the built-in pull-up resistors can reduce the number of the required components and the required
installation space.
Use of a built-in pull-up resistor can be specified for each bit of port 3, independently of the other bits, by the PUO3
bit of pull-up-resistor-option register (PUO) and the port 3 mode register (PM3). When the PUO3 bit is 1, the built-
in pull-up resistor for a pin specified by the PM3 (PM3n = 1, n = 0 to 7) is connected.
bit of pull-up-resistor-option register (PUO) and the port 3 mode register (PM3). When the PUO3 bit is 1, the built-
in pull-up resistor for a pin specified by the PM3 (PM3n = 1, n = 0 to 7) is connected.
If a pin is specified to be in the control mode, the built-in pull-up resistor for the pin is connected. (A built-in pull-
up resistor is connected to a pin that becomes an output pin during the control mode.) If you do not want to use
the built-in pull-up resistor for a pin in the control mode, reset the corresponding bit of the PM3 to 0 (output mode).
up resistor is connected to a pin that becomes an output pin during the control mode.) If you do not want to use
the built-in pull-up resistor for a pin in the control mode, reset the corresponding bit of the PM3 to 0 (output mode).
Fig. 5-19 Pull-Up-Resistor-Option Register Format
Remark Resetting the PUO2 bit to 00H can reduce the required current in the STOP mode.
0
7
PUO6
6
PUO5
5
PUO4
4
PUO3
3
PUO2
2
0
1
0
0
PUO
PUO3
Connected with port 3
Not connected with port 3
Specifies pull-up resistor connection of port 3
(00H when RESET is input)
0
1
RD
PM3n = 1
PM3n = 0
PM3n
n = 0 to 7
n = 0 to 7
Control (input)
Control (output)
Internal bus