Datasheet

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Digital Interface

Figure 3. BVDD Voltage Selection

2.2 Control Signals

There are a variety of control lines associated with the ADS855xEVM that are user accessible through

connectors J1, J4 and J5. The operating mode of the device determines which connectors are used to

control the converter operation, the conversion timing and then to obtain the digital results. Switch SW1

configures the basic operation of the device under test.

Figure 4. SW1 – Operational Controls

Options available on SW1 include Reference Enable, Serial or Parallel interface, Software or Hardware

control and BYTE or WORD data bus width. The figure above represents the silkscreen on the

ADS855xEVM. The default positions of the switch elements are indicated by the red blocks. All switch

positions except for REFen apply logic '0' to their respective control lines. These individual functions are

described in the following sections.

2.2.1 BYTE – WORD (SW1.1)

When Parallel mode is selected, SW1.1 controls the bus width of the output data. Switched to the right

(default – logic 0), the data bus is 16-bits wide, when switched to the left BYTE mode is enabled and two

8-bit read accesses to the data bus are required to obtain the full conversion result. Consult the datasheet

for a complete description of BYTE mode operation.

SLAU298–November 2009 ADS855xEVM

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