Remote High Limit

RDTS Measurement

TIME

ALERT mask set in

response to ARA

from master

LM89 ALERT pin

Status Register: RTDS High

LM89

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SNIS128D – AUGUST 2002 – REVISED JUNE 2014

Feature Description (continued)

Figure 7. ALERT Output As An Smbus Alert Temperature Response Diagram

9.3.3

T_CRIT_A Output And T_CRIT Limit

T_CRIT_A is activated when any temperature reading is greater than the limit preset in the critical temperature

setpoint register (T_CRIT), as shown in Figure 8. The Status Register can be read to determine which event

caused the alarm. A bit in the Status Register is set high to indicate which temperature reading exceeded the

T_CRIT setpoint temperature and caused the alarm, see Status Register (SR).

Local and remote temperature diodes are sampled in sequence by the A/D converter. The T_CRIT_A output and

the Status Register flags are updated after every Local and Remote temperature conversion. T_CRT_A follows

the state of the comparison, it is reset when the temperature falls below the setpoint RCS-TH. The Status

Register flags are reset only after the Status Register is read and if a temperature conversion(s) is/are below the

T_CRIT setpoint, as shown in Figure 8.

Figure 8. T_CRIT_A Temperature Response Diagram

9.3.4 Smbus Interface

The LM89 operates as a slave on the SMBus, so the SMBCLK line is an input and the SMBData line is bi-

directional. The LM89 never drives the SMBCLK line and it does not support clock stretching. According to

SMBus specifications, the LM89 has a 7-bit slave address. All bits A6 through A0 are internally programmed and

can not be changed by software or hardware. The LM89 and LM89-1 versions have the following SMBus slave

addresses:

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