MCP3912 datasheet(45/82 Pages) MICROCHIP

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 2014 Microchip Technology Inc.

DS20005348A-page 45

MCP3912

6.5

Continuous Communications,

Looping on Register Sets

The MCP3912 digital interface can process communi-

cations in Continuous mode without having to enter an

SPI command between each read or write to a register.

This feature allows the user to reduce communication

overhead to the strict minimum, which diminishes EMI

emissions and reduces switching noise in the system.

The registers can be grouped into multiple sets for con-

tinuous communications. The grouping of the registers

in the different sets is defined by the READ<1:0> and

WRITE bits that control the internal SPI communication

address pointer. For a graphical representation of the

WRITE bits, please see Table 8-2.

In the case of a continuous communication, there is

only one control byte on SDI to start the communication

after a CS pin falling edge. The part stays within the

same communication loop until the CS pin returns logic

high. The SPI internal register address pointer starts by

transmitting/receiving the address defined in the con-

trol byte. After this first transmission/reception, the SPI

internal register address pointer automatically incre-

ments to the next available address in the register set

for each transmission/reception. When it reaches the

last address of the set, the communication sequence is

finished. The address pointer automatically loops back

to the first address of the defined set and restarts a new

sequence with auto-increment (see Table 6-6). This

internal address pointer automatic selection allows the

following functionality:

• Read one ADC channel data, pairs of ADC

channels or all ADC channels continuously

• Continuously read the entire register map

• Continuously read or write each separate register

• Continuously read or write all configuration

registers

FIGURE 6-6:

Continuous Communication Sequences.

Don’t care

Continuous READ communication (24-bit format)

Don’t care

SCK

SDI

SDO

Hi-Z

CONTROL

BYTE

24x

ADDR

...

ADDR + n

Starts read sequence

at address ADDR

Complete READ sequence

ADDR + 1

24x

...

24x

ADDR

...

Complete READ sequence

ADDR + 1

24x

...

24x

ADDR + n

Continuous WRITE communication (24-bit format)

Don’t care

SCK

SDI

SDO

Hi-Z

CONTROL

BYTE

24x

ADDR

...

ADDR + n

Starts write sequence

at address ADDR

Complete WRITE sequence

ADDR + 1

24x

...

24x

ADDR

...

Complete WRITE sequence

ADDR + 1

24x

...

24x

ADDR + n

ADDR

ADDR + 1

...

ADDR + n

Complete

READ

sequence

Roll-over

ADDRESS SET

ADDR

ADDR + 1

...

ADDR + n

Complete

WRITE

sequence

Roll-over

ADDRESS SET

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