C8051T630 Datasheet, PDF (111/221 Pages) Silicon Laboratories – Mixed-Signal Byte-Programmable EPROM MCU

C8051T630/1/2/3/4/5
WEAKPUD
(Weak Pull-Up Disable)
PxMDOUT.x
(1 for push-pull)
(0 for open-drain)
XBARE
(Crossbar
Enable)
Px.x – Output
Logic Value
(Port Latch or
Crossbar)
PxMDIN.x
(1 for digital)
(0 for analog)
To/From Analog
Peripheral
Px.x – Input Logic Value
(Reads 0 when pin is configured as an analog I/O)
VDD
VDD
(WEAK)
PORT
PAD
GND
Figure 20.2. Port I/O Cell Block Diagram
20.1.3. Interfacing Port I/O to 5V Logic
All Port I/O configured for digital, open-drain operation are capable of interfacing to digital logic operating at
a supply voltage higher than VDD and less than 5.25 V. An external pullup resistor to the higher supply
voltage is typically required for most systems.
Important Note: In a multi-voltage interface, the external pullup resistor should be sized to allow a current
of at least 150 µA to flow into the Port pin when the supply voltage is between (VDD + 0.6 V) and (VDD +
1.0 V). Once the Port pin voltage increases beyond this range, the current flowing into the Port pin is mini-
mal.
Rev. 1.0
111