MCP3903 datasheet(32/54 Pages) MICROCHIP

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MCP3903

DS25048B-page 32

FIGURE 6-5:

Device Write (SPI Mode 1,1 - Clock Idles High).

6.7

Read Continuously Channel Data,

LOOPING ON ADDRESS SETS

If the user wishes to read back any of the ADC

channels continuously, or all channels continuously,

the internal address counter of the MCP3903 can be

set to loop on specific register sets. In this case, there

is only one control byte on SDI to start the

communication. The part stays within the same loop

until CS returns high.

This internal address counter allows the following

functionality:

• Read one ADC channel data continuously

• Read all ADC channel data continuously (all ADC

data can be independent or linked with

DRn_MODE settings)

• Read continuously the entire register map

• Read continuously each separate register

• Read continuously all configuration registers

• Write all configuration registers in one

communication (see Figure 6-6)

The STATUS/COM register contains the loop settings

for the internal address counter (READ<1:0>). The

internal address counter can either stay constant

(READ<1:0>=00) and continuously read the same

byte, or it can auto-increment and loop through the

map (READ<1:0>=11).

Each channel is configured independently as either a

16-bit or 24-bit data word, depending on the setting of

the corresponding WIDTH bit in the CONFIG register.

For continuous reading, in the case of WIDTH=0

(16-bit), the lower byte of the ADC data is not accessed

and the part jumps automatically to the following

address (the user does not have to clock out the lower

byte since it becomes undefined for WIDTH=0).

The following figure represents a typical continuous

read communication with the default settings

(DRMODE<1:0>=00, READ<1:0>=10) for both

WIDTH settings. This configuration is typically used for

power metering applications.

FIGURE 6-6:

Typical Continuous Read Communication.

SCK

SDI

SDO

R/W

A6 A5 A4 A3 A2 A1 A0

23 22 21 20 19 18

(ADDRESS) DATA

D6 D5 D4 D3 D2 D1

D16

DATA TRANSITIONS ON

THE FALLING EDGE

MCU AND MCP3901 LATCH

BITS ON THE RISING EDGE

HI-Z

D08

CH5

MCP3903 Datasheet(PDF) 32 Page - Microchip Technology

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