MAX17843ACB datasheet(59/131 Pages) MAXIM

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Battery-Management

UART Protocol Commands

HELLOALL Command

The purpose of the HELLOALL command is to initialize the

device addresses of all daisy-chained devices. The device

address is stored in the DA[4:0] bits of the ADDRESS reg-

ister. The highest address possible is 0x1F, so a maximum

of 32 devices can be addressed. The command must be

issued after POR to reinitialize all device addresses.

When the HELLOALL command is first sent by the host,

the address specified in the HELLOALL command is

stored to the DA[4:0] bits of the ADDRESS register in the

first daisy-chained device. The command is then forward-

ed to the next device in the chain, with the DA[4:0] bits of

the address byte incremented by 1, as shown in Table 27.

This continues in the upstack direction for each device.

The downstack communication path does not increment

the address. The advantage of the host choosing a first

address of 0x00 is that it is not necessary to write the first

address FA[4:0] to all the devices since the default value

of FA[4:0] is 0x00.

Note: The host should set the first

address so that no assigned device address increments

from 0x1F to 0x00 during the HELLOALL command.

The DA[4:0] value returned to the host is one greater

than the address assigned to the last device. Once this

last address is known, the host can determine how many

devices are in the daisy-chain, which is required for sub-

sequent READALL commands. A READALL command

should be used to verify the ADDRESS registers.

Special considerations exist if the host desires to use

internal loopback instead of external loopback. The

first HELLOALL command is not returned to the host

because the internal loopback bit for the top device has

not yet been written. If the number of devices is known

to the host, the host can use a WRITEDEVICE to set the

internal loopback bit on the last device and then verify

with a READALL command. If the number of devices is

unknown, the internal loopback bit must be set on the first

device, verified, and then cleared. It can then be set on

the second device and verified, and so on incrementally

until there is no response (end of stack). With the number

of devices known, the loopback bit can be reset on the

last device and all ADDRESS registers verified.

When a device receives a valid HELLOALL command, it

clears the ADDRUNLOCK bit of the DEVCFG1 register.

When this bit is 0, HELLOALL commands are ignored to

prevent inadvertently changing any device address. To

reconfigure the device address, the ADDRUNLOCK bit

must first be set to 1, or a POR event must occur. After

configuring the device addresses, they should be verified

using the READALL or ROLLCALL commands.

Table 27. HELLOALL Sequencing (z = Total Number of Devices)

HOST TX

DEVICE (n) RXL

DEVICE (n) TXU

HOST RX

Preamble

57h

00h

{0b000,ADDR[4:0]}

{0b000,ADDR[4:0]+n-1}

{0b000,ADDR[4:0]+n}

{0b000,ADDR[4:0]+z}

Stop

MAX17843

12-Channel, High-Voltage Smart Sensor

Data-Acquisition Interface

www.maximintegrated.com

Maxim Integrated │ 59

MAX17843ACB Datasheet(PDF) 59 Page - Maxim Integrated Products

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