
ADuC836
–10–
ADuC836
–11–
PIN FUNCTION DESCRIPTIONS (continued)
Pin No. Pin No.
52-Lead 56-Lead
MQFP CSP
Mnemonic
Type* Description
P1.4/AIN1
I
Primary ADC, Positive Analog Input
P1.5/AIN2
I
Primary ADC, Negative Analog Input
P1.6/AIN3
I
Auxiliary ADC Input or Muxed Primary ADC, Positive Analog Input
P1.7/AIN4/DAC
I/O
Auxiliary ADC Input or Muxed Primary ADC, Negative Analog Input.The voltage
output from the DAC can also be configured to appear at this pin.
5
4, 5
AVDD
S
Analog Supply Voltage, 3 V or 5 V
6
6, 7, 8
AGND
S
Analog Ground. Ground reference pin for the analog circuitry.
7
9
REFIN(–)
I
Reference Input, Negative Terminal
8
10
REFIN(+)
I
Reference Input, Positive Terminal
13
15
SS
I
Slave Select Input for the SPI Interface. A weak pull-up is present on this pin.
14
16
MISO
I/O
Master Input/Slave Output for the SPI Interface. A weak pull-up is present on this input pin.
15
17
RESET
I
Reset Input. A high level on this pin for 16 core clock cycles while the oscillator is
running resets the device.There is an internal weak pull-down and a Schmitt trigger
input stage on this pin.
16–19,
18–21,
P3.0–P3.7
I/O
P3.0–P3.7 are bidirectional port pins with internal pull-up resistors. Port 3 pins that
22–25
24–27
have 1s written to them are pulled high by the internal pull-up resistors, and in that
state can be used as inputs. As inputs, Port 3 pins being pulled externally low will
source current because of the internal pull-up resistors.When driving a 0-to-1 output
transition, a strong pull-up is active for two core clock periods of the instruction
cycle. Port 3 pins also have various secondary functions including:
P3.0/RXD
I/O
Receiver Data for UART Serial Port
P3.1/TXD
I/O
Transmitter Data for UART Serial Port
P3.2/INT0
I/O
External Interrupt 0.This pin can also be used as a gate control input to Timer 0.
P3.3/INT1
I/O
External Interrupt 1.This pin can also be used as a gate control input to Timer 1.
P3.4/T0/PWMCLK I/O
Timer/Counter 0 External Input. If the PWM is enabled, an external clock may be
input at this pin.
P3.5/T1
I/O
Timer/Counter 1 External Input
P3.6/WR
I/O
External Data Memory Write Strobe. Latches the data byte from Port 0 into an
external data memory.
P3.7/RD
I/O
External Data Memory Read Strobe. Enables the data from an external data memory
to Port 0.
20, 34, 48 22, 36, 51, DVDD
S
Digital Supply, 3 V or 5 V
21, 35, 47 23, 37, 38, DGND
S
Digital Ground. Ground reference point for the digital circuitry.
50
26
SCLOCK
I/O
Serial Interface Clock for either the I2C or SPI Interface. As an input, this pin is a
Schmitt-triggered input, and a weak internal pull-up is present on this pin unless it is
outputting logic low.This pin can also be directly controlled in software as a digital
output pin.
27
MOSI/SDATA
I/O
Serial Data I/O for the I2C Interface or Master Output/Slave Input for the
SPI Interface. A weak internal pull-up is present on this pin unless it is outputting
logic low.This pin can also be directly controlled in software as a digital output pin.
28–31
30–33
P2.0–P2.7
I/O
Port 2 is a bidirectional port with internal pull-up resistors. Port 2 pins that have 1s
36–39
39–42
(A8–A15)
written to them are pulled high by the internal pull-up resistors, and in that state can
(A16–A23)
be used as inputs. As inputs, Port 2 pins being pulled externally low will source current
because of the internal pull-up resistors.
Port 2 emits the high order address bytes during fetches from external program memory
and middle and high order address bytes during accesses to the 24-bit external data
memory space.
32
34
XTAL1
I
Input to the Crystal Oscillator Inverter
33
35
XTAL2
O
Output from the Crystal Oscillator Inverter. (See the Hardware Design Considerations
section for description.)
REV. A