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5
Operation
5.1
Pushbuttons and Indicator LEDs
Power
Connectors
DB9
Input Circuitry
ADS5240/42
Input Circuitry
Output Connector
Clock
Driver
Clock
SMA
Micro
RS232
−TTL
Green LED
Green LED
Green LED
Green LED
SW3
SW2
SW1
Int/Ext Reference LED (on = Int)
Serial Interface (on = data)
Power Down LED (on = Powered Down)
Reset LED
Int/Ext Reference Select pushbutton
Power Down Puchbutton
Reset Pushbutton
5.2
Serial Data In
5.3
Accessing the Internal Registers
Operation
When power is applied to the board, the EVM performs an initialization sequence that sets the initial
operation of the ADS5240/42. The Ref LED lights up to signify that the Int/Ext (bar over Ext) reference is
set to internal. The RST LED is illuminated while a reset pulse is provided to the ADS5240/42 to reset the
device for proper operation. The EVM is now operational and if connected to the ADSDESer-50EVM and
reset pushbutton is pressed on the deserializer board, parallel data should be available on each channel
output and a clock should be present on the clock output.
The ADS5240/42EVM has three pushbuttons and four indicator LEDs. The pushbuttons and their
corresponding LEDs are defined as follows:
•
SW1 - RST - Reset of the ADS5240/42 device. (Resets only the ADS517x device)
•
SW2 – PD– Power Down of the device. (LED on signifies complete device in power down)
•
SW3 – Ref– Internal / External (bar over External) Reference Selection. (LED on signifies Internal)
The fourth LED, SDI, when illuminated signifies that data has been received from the PC through the
serial link.
Figure 1. Evaluation Board Overview
The Serial Data In (DB-9) connector is used to connect the EVM to a PC for accessing the internal
registers of the ADS5240/42 device. This allows extended flexibility of the device beyond the simple
power-up mode.
The ADS5240/42 family has internal registers that offer flexibility to the end user. In order to facilitate the
ease of accessing these registers, the evaluation program is used. With the combination of a serial port on
a PC, a serial link cable (provided), and the ADS5240/42EVM, the user has the ability to access the
internal registers on the ADS5240/42 family of data converters.
6
SBAU116 – October 2005
