PS501 datasheet(19/42 Pages) MICROCHIP

19 / 42 page

 2004 Microchip Technology Inc.

DS21818C-page 19

PS501

8.0

SMBus/SBData INTERFACE

The PS501 uses a two-pin System Management Bus

(SMBus) protocol to communicate to the Host. One pin

is the clock and one pin is the data. The SMBus port

responds to all commands in the Smart Battery Data

Specification (SBData). To receive information about

the battery, the Host sends the appropriate commands

to the SMBus port. Certain alarms, warnings and

charging information may be sent to the Host by the

PS501 automatically. The SMBus protocol is explained

this

chapter.

The

SBData

command

set

summarized in Table 8-1.

The PS501 SMBus communications port is fully com-

pliant with the System Management Bus Specification,

Version 1.1 and supports all previous and new

requirements, including bus time-outs (both slave and

master), multi-master arbitration and collision detec-

tion/recovery. The SMBus port serves as a slave for

both read and write functions, as well as a master for

write word functions. SMBus slave protocols supported

include read word, write word, read block and write

block. Master mode supports write word protocols. The

PS501 meets and exceeds the Smart Battery Data

Specification, Version 1.1/1.1a requirements. The

PS501 is compliant with System Management Bus

Specification 1.0.

The PS501 fully implements the Smart Battery Data

(SBData) Specification v1.1. The SBData Specification

defines the interface and data reporting mechanism for

an SBS compliant Smart Battery. It defines a consistent

set of battery data to be used by a power management

system to improve battery life and system run-time,

while providing the user with accurate information. This

is accomplished by incorporating fixed, measured,

calculated and predicted values, along with charging

and alarm messages, with a simple communications

mechanism between a Host system, Smart Batteries

and a Smart Charger.

The PS501 provides full implementation of the SBData

set with complete execution of all the data functions,

including sub-functions and control bits and flags, com-

pliance to the accuracy and granularity associated with

particular data values and proper SMBus protocols and

timing.

8.1

SBData Function Description

The following subsections document the detailed

operation of all of the individual SBData commands.

8.1.1

ManufacturerAccess (0x00)

Internal use only.

8.1.2

RemainingCapacityAlarm (0x01)

Sets or reads the low capacity alarm value. Whenever

the remaining capacity falls below the low capacity

alarm value, the Smart Battery sends alarm warning

messages

the

SMBus

Host

with

the

REMAINING_CAPACITY_ALARM

bit

set.

low

capacity alarm value of ‘0’ disables this alarm.

8.1.3

RemainingTimeAlarm (0x02)

Sets or reads the remaining time alarm value.

Whenever the AverageTimeToEmpty falls below the

remaining time value, the Smart Battery sends alarm

warning messages to the SMBus Host with the

REMAINING_TIME_ALARM bit set. A remaining time

value of ‘0’ disables this alarm.

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