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REV. PrB
ADuC842
–7–
PIN F UNC T ION D E SC R IPT IONS
Mnemonic
T ype F unction
D V
D D
A V
D D
C
R E F
V
R E F
P
P
I
I/O
Digital Positive Supply Voltage, 3 V or 5 V Nominal
Analog Positive Supply Voltage, 3 V or 5 V Nominal
Decoupling Input for On-Chip Reference. Connect 0.1 μF between this pin and AGND.
Reference Input/Output. T his pin is connected to the internal reference through a series resistor
and is the reference source for the analog-to-digital converter. T he nominal internal reference
voltage is 2.5 V and this appears at the pin. T his pin can be overdriven by an external reference.
Analog Ground. Ground Reference point for the analog circuitry.
Port 1 is an 8-bit Input Port only. Unlike other Ports, Port 1 defaults to Analog Input Mode, to
configure any of these Port Pins as a digital input, write a “0” to the port bit. Port 1 pins are mul-
tifunction and share the following functionality.
Analog Inputs. Eight single-ended analog inputs. Channel selection is via ADCCON2 SFR.
T imer 2 Digital Input. Input to T imer/Counter 2. When Enabled, Counter 2 is incremented in
response to a 1 to 0 transition of the T 2 input.
Digital Input. Capture/Reload trigger for Counter 2 and also functions as an Up/Down control
input for Counter 2.
Slave Select Input for the SPI Interface
User Selectable, I
2
C-Compatible or SPI Data Input/Output Pin
Serial Clock Pin for I
2
C-Compatible or SPI Serial Interface Clock
SPI Master Output/Slave Input Data I/O Pin for SPI Interface
SPI Master Input/Slave Output Data I/O Pin for SPI Serial Interface
Voltage Output from DAC0
Voltage Output from DAC1
Digital Input. A high level on this pin for 24 master clock cycles while the oscillator is running
resets the device.
Port 3 is a bidirectional port with internal pull-up resistors. Port 3 pins that have 1s written to
them are pulled high by the internal pull-up resistors, and in that state they can be used as inputs.
As inputs Port 3 pins being pulled externally low will source current because of the internal pull-
up resistors. Port 3 pins also contain various secondary functions which are described below.
PWM Clock Input
PMW0 Voltage Output. PWM outputs can be configured to use ports 2.6 & 2.7 or 3.4 and 3.3
PMW1 Voltage Ouput. See CFG832 Register for further Information.
Receiver Data Input (Asynchronous) or Data Input/Output (Synchronous) of Serial (UART ) Port
T ransmitter Data Output (Asynchronous) or Clock Output (Synchronous) of Serial (UART ) Port
Interrupt 0, programmable edge or level triggered Interrupt input, which can be programmed to
one of two priority levels. T his pin can also be used as a gate control input to T imer 0.
Interrupt 1, programmable edge or level triggered Interrupt input, which can be programmed to
one of two priority levels. T his pin can also be used as a gate control input to T imer 1.
T imer/Counter 0 Input
T imer/Counter 1 Input
Active low Convert Start Logic input for the ADC block when the external Convert start function is enabled.
A low-to-high transition on this input puts the track/hold into its hold mode and starts conversion.
Write Control Signal, Logic Output. Latches the data byte from Port 0 into the external data
memory.
Read Control Signal, Logic Output. Enables the external data memory to Port 0.
Output of the Inverting Oscillator Amplifier
Input to the inverting oscillator amplifier and input to the internal clock generator circuits.
Digital Ground. Ground reference point for the digital circuitry.
Port 2 is a bidirectional port with internal pull-up resistors. Port 2 pins that have 1s written to them are
pulled high by the internal pull-up resistors, and in that state they can 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 external 24-bit external data memory space.
A G N D
P1.0–P1.7
G
I
AD C 0–AD C 7 I
T 2
I
T 2E X
I
S S
SD AT A
SC L OC K
M OSI
M ISO
D AC 0
D AC 1
R E SE T
I
I/O
I/O
I/O
I/O
O
O
I
P3.0–P3.7
I/O
PW M C
PW M 0
PW M 1
R xD
T xD
INT 0
I
O
O
I/O
O
I
INT 1
I
T 0
T 1
C ON V ST
I
I
I
W R
O
R D
X T AL 2
X T AL 1
D G N D
P2.0–P2.7
(A8–A15)
O
O
I
G
I/O
(A16–A23)