Intel 8XC196MC User Manual
14-3
SPECIAL OPERATING MODES
14.2 REDUCING POWER CONSUMPTION
Both power-saving modes conserve power by disabling portions of the internal clock circuitry
(Figure 14-1). The following paragraphs describe both modes in detail.
(Figure 14-1). The following paragraphs describe both modes in detail.
P1_DIR (MH)
P2_DIR
P5_DIR
P7_DIR (MD)
P2_DIR
P5_DIR
P7_DIR (MD)
1F9BH
1FD2H
1FF3H
1FD3H
1FD2H
1FF3H
1FD3H
Port
x
Direction
Each bit of P
x
_DIR controls the direction of the corresponding pin.
Clearing a bit configures a pin as a complementary output; setting
a bit configures a pin as an input or open-drain output. (Open-
drain outputs require external pull-ups.)
a bit configures a pin as an input or open-drain output. (Open-
drain outputs require external pull-ups.)
P1_MODE(MH)
P2_MODE
P5_MODE
P7_MODE(MD)
P2_MODE
P5_MODE
P7_MODE(MD)
1F99H
1FD0H
1FF1H
1FD1H
1FD0H
1FF1H
1FD1H
Port
x
Mode
Each bit of P
x
_MODE controls whether the corresponding pin
functions as a standard I/O port pin or as a special-function
signal. Setting a bit configures a pin as a special-function signal;
clearing a bit configures a pin as a standard I/O port pin.
signal. Setting a bit configures a pin as a special-function signal;
clearing a bit configures a pin as a standard I/O port pin.
P1_REG (MH)
P2_REG
P5_REG
P7_REG (MD)
P2_REG
P5_REG
P7_REG (MD)
1F9DH
1FD4H
1FF5H
1FD5H
1FD4H
1FF5H
1FD5H
Port
x
Data Output
For an input, set the corresponding P
x
_REG bit.
For an output, write the data to be driven out by each pin to the
corresponding bit of P
corresponding bit of P
x
_REG. When a pin is configured as
standard I/O (P
x
_MODE.
y
= 0), the result of a CPU write to
P
x
_REG is immediately visible on the pin. When a pin is
configured as a special-function signal (P
x
_MODE.
y
= 1), the
associated on-chip peripheral or off-chip component controls the
pin. The CPU can still write to P
pin. The CPU can still write to P
x
_REG, but the pin is unaffected
until it is switched back to its standard I/O function.
This feature allows software to configure a pin as standard I/O
(clear P
(clear P
x
_MODE.
y
), initialize or overwrite the pin value, then
configure the pin as a special-function signal (set P
x
_MODE.
y
). In
this way, initialization, fault recovery, exception handling, etc., can
be done without changing the operation of the associated
peripheral.
be done without changing the operation of the associated
peripheral.
Table 14-2. Operating Mode Control and Status Registers (Continued)
Mnemonic
Address
Description