MCP3464T-ESLASHST datasheet(60/108 Pages) MICROCHIP

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MCP3461/2/4

DS20006180D-page 60

 2019-2021 Microchip Technology Inc.

6.2.2

DEVICE ADDRESS BITS (CMD[7:6])

The SPI interface of the MCP3461/2/4 devices is

addressable, which means that multiple devices can

communicate on the same SPI bus with only one chip

select line for all devices. Each device communication

starts by a CS falling edge, followed by the clocking of

the device address (CMD[7:6]). Each device contains

an internal device address which the device can

respond to.

This device address is coded on two bits, so four possible

addresses are available. The address is hard-coded

within the device and should be determined at the order-

ing of the device. The device address is part of the device

markings to avoid potential confusion (see Section 9.1

“Package Marking Information(2)”). When the

CMD[7:6] bits match the device address, the communi-

cation proceeds and the part will execute the commands

defined in the control byte and its subsequent data bytes.

When the CMD[7:6] bits do not correspond to the

device address hard-coded in the device, the com-

mand is ignored. In this case, the SDO output will

become high-impedance, which prevents bus conten-

tion errors when multiple devices are connected on the

same SPI bus (see Figure 6-3). The user has to exit

from this communication through a CS rising edge to

be able to launch another command.

6.2.3

COMMAND ADDRESS BITS

(CMD[5:2])

The COMMAND byte contains four address bits

(CMD[5:2]) that can serve two purposes. In case of a

case of a Fast command, they determine which Fast

command is executed by the device. In case of a Write

command on a read-only register, the command is not

executed and the communication should be aborted

(CS rising edge) to place another command. All

registers can be read; there is no undefined address in

the register map.

6.2.4

COMMAND-TYPE BITS (CMD[1:0])

The last two bits of the COMMAND byte define the

command type. These bits are an extension of the typical

read/write bits present in most SPI communication proto-

cols. The two bits define four possible command types:

Incremental Write, Incremental Read, Static Read and

Fast command. Changing command type within the

same communication (while CS is logic low) is not

possible. The communication has to be stopped (CS

rising edge) and restarted (CS falling edge) to change its

command type. The list of possible commands, their type

and their possible command addresses are described in

Table 6-1.

TABLE 6-1:

COMMAND TYPES DESCRIPTION TABLE

CMD[5:2]

CMD[1:0]

Command Description

0xxx

Don’t Care

100x

Don’t Care

1010

ADC Conversion Start/Restart Fast Command (Overwrites ADC_MODE[1:0] = 11)

1011

ADC Standby Mode Fast Command (Overwrites ADC_MODE[1:0] = 10)

1100

ADC Shutdown Mode Fast Command (Overwrites ADC_MODE[1:0] = 00)

1101

Full Shutdown Mode Fast Command (Overwrites CONFIG0[7:0] = 0x00)

1110

Device Full Reset Fast Command (Resets Whole Register Map to Default Value)

1111

Don’t Care

ADDR

Static Read of Register Address, ADDR

ADDR

Incremental Write Starting at Register Address, ADDR

ADDR

Incremental Read Starting at Register Address, ADDR

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