MCP3918 datasheet(48/88 Pages) MICROCHIP

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MCP3918

DS20005287A-page 48

 2014 Microchip Technology Inc.

6.5.1

CONTINUOUS READ

The STATUSCOM register contains the loop settings

for the internal register address pointer (READ<1:0>

bits and WRITE bit). For the Continuous Read modes,

the address selection can take the four following

values:

No SDI data coming after the Control byte is

considered during a continuous read communication.

The following figures represent a typical, continuous

read

communication

with

the

default

settings

(READ<1:0> = 10, WIDTH_DATA<1:0> = 01) for SPI

Mode 0,0 (Figure 6-7) and SPI Mode 1,1 (Figure 6-8).

In SPI Mode (1,1), the SDO pin stays in the last state

(LSB of previous data) after a complete reading, which

also allows seamless Continuous Read mode (see

Figure 6-8).

FIGURE 6-7:

Typical Continuous Read Communication (WIDTH_DATA<1:0> = 01, SPI Mode 0,0).

FIGURE 6-8:

Typical Continuous Read Communication (WIDTH_DATA<1:0> = 01, SPI Mode 1,1).

TABLE 6-1:

ADDRESS SELECTION IN

CONTINUOUS READ

READ<1:0>

for Continuous Read

Communications

Static (No incrementation)

Groups

Types (Default)

Full Register Map

Note:

For continuous reading of ADC data in

SPI Mode 0,0 (see Figure 6-7), once the

data has been completely read after a

data ready pulse, the SDO pin will take the

MSB value of the previous data at the end

of the reading (falling edge of the last SCK

clock). If SCK stays idle at logic low (by

definition of Mode 0,0), the SDO pin will

be updated at the falling edge of the next

Data Ready pulse (synchronously with the

DR pin falling edge with an output timing

of tDODR) with the new MSB of the data

corresponding to the Data Ready pulse.

This mechanism allows the MCP3918 to

continuously read ADC data outputs

seamlessly, even in SPI Mode (0,0).

Don’t care

SCK

SDI

SDO

Hi-Z

0x01

24x

Starts read sequence at

address 00000

24x

Don’t care

Complete READ sequence on

new ADC output channel

Complete READ sequence on

the ADC output channel

DATA_CH0

Stays at

DATA_CH<0>

DATA_CH0

Don’t care

SCK

SDI

SDO

Hi-Z

0x01

24x

Starts read sequence at

address 00000

24x

Don’t care

DATA_CH0

<23>

New data

DATA_CH0

<23>

Old data

MCP3918 Datasheet(PDF) 48 Page - Microchip Technology

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