–2–
AN-744
–3–
AN-744
RESET pin on the ADuC7026 is Schmitt-triggered inter-
nally there is no need to use an external Schmitt trigger
on this pin.
When inserted the IRQ0 push-button switch drives
P0.4/IRQ0 high. This can be used to initiate an external
interrupt 0.
To enter serial download mode the user must pull the
P0.0/BM pin low while reset is toggled. On the evalua-
tion board, serial download mode can be easily initiated
by holding down the serial download push-button (S2)
while inserting and releasing the reset button (S3) as
illustrated in Figure 1.
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Figure 1. Entering Serial Download Mode
on the Evaluation Board
Power Indicator/General-Purpose LEDs
A red power LED (D3) is used to indicate that a sufficient
supply is available on the board. A general-purpose LED
(D2) is directly connected to P4.2 of the ADuC7026. When
P4.2 is cleared the LED will be turned on, and when P4.2
is set, the LED will be turned off.
Analog I/O Connections
All analog I/O are brought out on header J3.
ADC0 and ADC1 are buffered using an AD8606 to evaluate
single-ended and pseudo differential mode. A potentiometer
can be connected to ADC0 buffered.
ADC3 and ADC4 can be buffered with a single-ended to
differential op amp on board, the AD8132, used to evalu-
ate the ADC in fully differential mode.
ADC2 and ADC5 to ADC11 are not buffered. Be sure to
follow the data sheet recommendation when connecting
signals to these inputs.
DAC1 can be used to control the brightness of the green
LED D1, when connected via the S1 switch.
General-Purpose Prototype Area
General-purpose prototype areas are provided at the
bottom of the evaluation board for adding external
components as required in the user’s application. As can
be seen from the layout AV
DD
, AGND, V
DDIO
, and DGND
tracks are provided in this prototype area.
External Memory and Latch Footprint
Footprint for a 32 kB
16 static RAM (CY7C1020CV33)
and 16-bit latch is also on board. See External Memory
Interface section.
DIP SWITCH LINK OPTIONS
S1-1 VREF
Function: Connects the output of the 2.5 V external refer-
ence (ADR291) to the VREF pin (Pin 55) of the
ADuC7026.
Use: Slide S1-1 to the on position to connect the
external reference to the ADuC7026.
Slide S1-1 to the off position to use the internal
2.5 V reference or a different external reference
on VREF pin of J3 header.
S1-2 VOCM
Function: Connects 1.67 V to the V
OCM
pin of the AD8132.
No extra dc voltage is required on the board
to use the ADC in differential mode.
Use: Slide S1-2 to the on position to connect V
OCM
of the differential amplifier to 1.67 V, divided
output of the ADR291 reference.
Slide S1-2 to the off position to use a different
voltage for V
OCM
by connecting a dc voltage to
the V
OCM
pin of J3 header. Note that V
OCM
value
is dependent on reference value as shown in
Table 1.
Table 1. V
OCM
Range
V
REF
V
OCM
min
V
OCM
max
2.5 V 1.25 V
2.05 V
2.048 V 1.024 V
2.276 V
1.25 V 0.75 V
2.55 V
S1-3 POT
Function: Connects the potentiometer output to ADC0.
This input is buffered by an AD8606. This is
for demonstration purposes.
Use: Slide S1-3 to the on position to connect the
potentiometer to the op amp of ADC0 input
channel.
Slide S1-3 to the off position to use ADC0
input on J3 header.
S1-4 ADC3
Function: Brings out ADC3 (Pin 64) on J3 header.
Use: Slide S1-6 to the on position to connect
directly ADC3 of J3 header to ADC3 pin
(Pin 64) of the ADuC7026.
Slide S1-6 to the off position to disconnect
ADC3 of J3 header from ADC3 pin (Pin 64) of
the ADuC7026.
REV. 0
REV. 0
