ADUC834 Analog Devices, ADUC834 Datasheet - Page 66

• Manufacturer Part Number: ADUC834
• Description: Precision Analog Microcontroller: 1MIPS 8052 MCU + 62kB Flash + 16/24-Bit ADC + 12-Bit DAC
• Manufacturer: Analog Devices

Specifications of ADUC834

• Mcu Core: 8052
• Mcu Speed (mips): 1
• Sram (bytes): 2304Bytes
• Gpio Pins: 34
• Adc # Channels: 4
• Other: PWM

ADuC834
If the user plans to connect fast logic signals (rise/fall time < 5 ns)
to any of the ADuC834’s digital inputs, add a series resistor to
each relevant line to keep rise and fall times longer than 5 ns at
the ADuC834 input pins. A value of 100 Ω or 200 Ω is usually
sufficient to prevent high speed signals from coupling capaci-
tively into the ADuC834 and affecting the accuracy of ADC
conversions.
ADuC834 System Self-Identification
In some hardware designs, it may be an advantage for the
software running on the ADuC834 target to identify the host
MicroConverter. For example, code running on the ADuC834
may also be used with the ADuC824 or the ADuC816, and is
required to operate differently.
b.
a.
c.
Figure 64. System Grounding Schemes
PLACE ANALOG
COMPONENTS
PLACE ANALOG
PLACE ANALOG
COMPONENTS
COMPONENTS
HERE
AGND
AGND
HERE
HERE
GND
PLACE DIGITAL
COMPONENTS
PLACE DIGITAL
PLACE DIGITAL
COMPONENTS
COMPONENTS
HERE
HERE
HERE
DGND
DGND
–66–
The CHIPID SFR is a read-only register located at SFR
address C2H. The upper nibble of this SFR designates the
MicroConverter within the Σ-∆ ADC family. User software can
read this SFR to identify the host MicroConverter and thus
execute slightly different code if required. The CHIPID SFR reads
as follows for the Σ-∆ ADC family of MicroConverter products.
Clock Oscillator
As described earlier, the core clock frequency for the ADuC834
is generated from an on-chip PLL that locks onto a multiple
(384 times) of 32.768 kHz. The latter is generated from an
internal clock oscillator. To use the internal clock oscillator,
connect a 32.768 kHz parallel resonant crystal between XTAL1
and XTAL2 pins (32 and 33) as shown in Figure 65.
As shown in the typical external crystal connection diagram in
Figure 65, two internal 12 pF capacitors are provided on-chip.
These are connected internally, directly to the XTAL1 and
XTAL2 pins, and the total input capacitances at both pins is
detailed in the Specification section of this data sheet. The value
of the total load capacitance required for the external crystal
should be the value recommended by the crystal manufacturer
for use with that specific crystal. In many cases, because of the
on-chip capacitors, additional external load capacitors will not
be required.
To facilitate in-circuit programming, plus in-circuit debug and
emulation options, users will want to implement some simple
connection points in their hardware that will allow easy access
to Download, Debug, and Emulation modes.
ADuC836
ADuC834
ADuC824
ADuC816
Figure 65. External Parallel Resonant Crystal
Connections Other Hardware Considerations
32.768kHz
XTAL2
XTAL1
32
33
12pF
12pF
ADuC834
CHIPID = 3xH
CHIPID = 2xH
CHIPID = 0xH
CHIPID = 1xH
TO INTERNAL
PLL
REV. A