Cirrus-logic CRD5378 Manual do Utilizador descarregar pdf (Página 26)

CRD5378

26 DS639RD2

2.3.3.2 I

C - SCL, SDA, Bypass

The I

telemetry connections to CRD5378 transmit and receive through RS-485 twisted pairs. Because

signals passing through the transceivers are actively buffered, full I

C bus arbitration and error detection

cannot be used (i.e. high-impedance NACK).

The I

C inputs and outputs can be externally wired to create either a daisy chain or a bus type network,

depending how the telemetry system is to be implemented. Analog switches included on CRD5378 can

bypass the I

C signals to create a bus network from a daisy chain network following address assignment.

When CRD5378 is used in a distributed measurement network, each node must have a unique address.

This address is used to transmit individual configuration commands and tag the source of returned con-

version data. Address assignment can be either dynamic or static, depending how the telemetry system

is to be implemented.

Dynamic address assignment uses daisy-chained I

C connections to assign an address to each mea-

surement node. Once a node receives an address, it enables the I

C bypass switches to the next node

so it can be assigned an address.

Static address assignment has a serial number assigned to each node during manufacturing. When

placed in the network the location is recorded and a master list of serial numbers vs. location is main-

tained. Alternately, a location dependent serial number can be assigned during installation.

2.3.4 UART Connection

A UART connection on CRD5378 provides a low-speed standardized connection for telemetry solutions

not using I

C. UART connections are provided for custom programming convenience only and are not di-

rectly supported by the CRD5378 PC evaluation software or microcontroller firmware.

Specification Value

I2C Inputs, 2 wires each SCL±, SDA±

I2C Outputs, 2 wires each BYP_SCL±, BYP_SDA±

I2C Bypass Switch Control BYP_EN

Specification Value

UART Connections, 2 wires each TX/GND, RX/GND

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Cirrus-logic CRD5378 Manual do Utilizador Página 26