C8051F120/1/2/3/4/5/6/7
232
Rev. 1.2
19.2.3. Configuring Port Pins as Digital Inputs
A Port pin is configured as a digital input by setting its output mode to “Open-Drain” and writing a logic 1 to the
associated bit in the Port Data register. For example, P7.7 is configured as a digital input by setting P7MDOUT.7 to a
logic 0 and P7.7 to a logic 1.
19.2.4. Weak Pull-ups
By default, each Port pin has an internal weak pull-up device enabled which provides a resistive connection (about
100 k
Ω
) between the pin and VDD. The weak pull-up devices can be globally disabled by writing a logic 1 to the
Weak Pull-up Disable bit, (WEAKPUD, XBR2.7). The weak pull-up is automatically deactivated on any pin that is
driving a logic 0; that is, an output pin will not contend with its own pull-up device.
19.2.5. External Memory Interface
If the External Memory Interface (EMIF) is enabled on the High ports (Ports 4 through 7), EMIFLE (XBR2.5) should
be set to a logic 0.
If the External Memory Interface is enabled on the High ports and an off-chip MOVX operation occurs, the External
Memory Interface will control the output states of the affected Port pins during the execution phase of the MOVX
instruction, regardless of the settings of the Port Data registers. The output configuration of the Port pins is not
affected by the EMIF operation, except that Read operations will explicitly disable the output drivers on the Data Bus
during the MOVX execution. See
Section “18. EXTERNAL DATA MEMORY INTERFACE AND ON-CHIP
XRAM” on page 199
for more information about the External Memory Interface.
Summary of Contents for C8051F120
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