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Conversions are initiated on the falling edge of the Convert Start signal. It is critical when measuring large
amplitude and/or high-frequency input signals that the user provide a clean, low-jitter Convert Start pulse.
The Convert Start signal can be applied to the ADS8481 from the decoder outputs or from connector P3
pin 17. Address decoder SN74ACH138 is used to generate the Read (RD) and Convert Start (CONVST)
signals to the converter. Jumpers W3 and W4 allow the user to assign these two signals to different
addresses in memory. This allows the stacking of up to two ADS8481EVMs into processor memory. See
Table 4
for jumper settings. If the user applies a Convert Start signal directly on P3 pin 17, then be sure to
short W6 pins 1-2. This bypasses the decoder output selected by the W4.
Note that the evaluation module does not allow the Chip Select (CS) line of the converter to be assigned
to different memory locations. Therefore, it is suggested that the CS line be grounded or wired to an
appropriate signal of the user's processor.
Reference
Designator
W1
Set digital buffer supply voltage to +5 V
Set digital buffer supply voltage
W2
Apply inverted BUSY to INTC signal to +3.3 V
Apply BUSY signal to INTC signal
W3
Set RD signal to add[0x3]
Set RD signal to add[0x4]
W4
Set CONVST signal to add[0x1]
Set CONVST signal to add[0x2]
W5
Set DC_CS to CS of ADS8481
W6
Set DC_CONVST to CONVST of ADS8481
Set decoder output to CONVST of ADS8481
(1)
Indicates factory-installed option.
The data bus is available at connector P2; see
Description
Data bit 0
Data bit 1
Data bit 2
Data bit 3
Data bit 4
Data bit 5
Data bit 6
Data bit 7
Data bit 8
Data bit 9
Data bit 10
Data bit 11
Data bit 12
Data bit 13
Data bit 14
Data bit 15
Data bit 16
Data bit 17
SLAU182A – June 2006 – Revised September 2006
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Table 4. Jumper Position
Description
Table 5
Table 5. Data Bus Connector P2
Signal Name
Connector Pin No.
DB0
P2.1
DB1
P2.3
DB2
P2.5
DB3
P2.7
DB4
P2.9
DB5
P2.11
DB6
P2.13
DB7
P2.15
DB8
P2.17
DB9
P2.19
DB10
P2.21
DB11
P2.23
DB12
P2.25
DB13
P2.27
DB14
P2.29
DB15
P2.31
DB16
P2.33
DB17
P2.35
Installed
Not Installed
Installed
Not installed
Installed
Not installed
Installed
Not Installed
Installed
Installed
Not installed
for pinout information.
Signal Name
P2.2
GND
P2.4
GND
P2.6
GND
P2.8
GND
P2.10
GND
P2.12
GND
P2.14
GND
P2.16
GND
P2.18
GND
P2.20
GND
P2.22
GND
P2.24
GND
P2.26
GND
P2.28
GND
P2.30
GND
P2.32
GND
P2.34
GND
P2.36
GND
Digital Interface
Pin No.
1-2
2-3
(1)
Not installed
Installed
(1)
Not installed
Installed
(1)
Not installed
Installed
(1)
Not installed
Installed
(1)
N/A
Not installed
(1)
Installed
Description
Ground
Ground
Ground
Ground
Ground
Ground
Ground
Ground
Ground
Ground
Ground
Ground
Ground
Ground
Ground
Ground
Ground
Ground
ADS8481EVM
5
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