SE97BTP datasheet(12/53 Pages) NXP

12 / 53 page

SE97B_1

Product data sheet

Rev. 01 — 27 January 2010

12 of 53

NXP Semiconductors

SE97B

DDR memory module temp sensor with integrated SPD

Table 5 shows the default values and the example value to be programmed to these

registers.

7.7 SMBus TIMEOUT

The SE97B supports SMBus TIMEOUT feature. If the host holds SCL LOW more than

35 ms, the SE97B would reset its internal state machine to the bus IDLE state to prevent a

system bus hang-up. This feature is turned on by default and release SDA. The SMBus

TIMEOUT can be disabled by writing a ‘1’ to SMBUS[7].

Remark: When SMBus TIMEOUT is enabled, the I2C-bus minimum bus speed is limited

by the SMBus TIMEOUT specification limit of 10 kHz.

The SE97B has no SCL driver, so it cannot hold the SCL line LOW.

7.8 SMBus Alert Response Address (ARA)

The SE97B supports SMBus ALERT when it is programmed for the Interrupt mode and

when the EVENT polarity bit is set to ‘0’. In Comparator mode or when the EVENT polarity

bit is set to ‘1’, the SMBus ALERT address is not acknowledged. The EVENT pin can be

ANDed with other EVENT or interrupt signals from other slave devices to signal their

intention to communicate with the host controller. When the host detects EVENT or other

interrupt signal LOW, it issues an ARA to which a slave device would respond with its

address. When there are multiple slave devices generating an ALERT the SE97B

performs bus arbitration with the other slaves. If it wins the bus, it responds to the ARA

and then clears the EVENT pin. This feature is turned off by default and can be enabled

by writing a ‘0’ to SMBUS[0].

Remark: Either in comparator mode or when the SE97B crosses the critical temperature,

the host must also read the EVENT status bit and provide remedy to the situation by

bringing the temperature to within the alarm window or below the critical temperature if

that bit is set. Otherwise, the EVENT pin will not get de-asserted.

Table 5.

Registers to be initialized

Default value

Example value

Description

01h

0000h

0209h

Configuration register

• hysteresis = 1.5 °C

• EVENT output = Interrupt mode

• EVENT output is enabled

02h

0000h

0550h

Upper Boundary Alarm Trip register = 85

°C

03h

0000h

1F40h

Lower Boundary Alarm Trip register =

−20 °C

04h

0000h

05F0h

Critical Alarm Trip register = 95

°C

22h

21h

SMBus register = no change

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